Since flights to Mexico City from the US and Canada are usually quite cheap this time of year as well, this could be a perfect short cultural holiday. This city has great shopping, dining, and nightlife, and the central historic and tourist districts are far safer than most people would expect. There are ruins just out of town as well, so a bit of everything is available.
You might also consider Malaysia and perhaps a stop in Singapore. Malaysia is actually more modern than Thailand so everything is easy and reliable. They have cheap VIP buses that are very comfortable. Penang in the north is really nice and also interesting. Kuala Lumpur is a modern and pleasant big city. A bit south of that is the colonial town of Malacca, which is also very nice and worth a look. Going south from there you can reach Singapore in a few hours, and that is an amazing city, although accommodation there is expensive.
As for alternatives you might consider Argentina, where of course it will be late spring in November. Buenos Aires is a wonderful city and recently they’ve been going through a financial meltdown again so their currency has dropped a lot, making things unusually cheap again. You could spend 3 or 4 days in Buenos Aires and the rest in the Mendoza wine country or Iguazu Falls or Bariloche for some adventure. From everything I have heard it’s all safe and civil there, so it’s just a matter of the local currency going down in value.
Adrenaline junkies should make for Tasmania’s Franklin-Gordon Wild Rivers National Park for roaring waterways and world-class river rafting. Punctuate your trip by exploring the surrounding scenery, from rocky gorges and mountains to tangled emerald rainforests. In Alta the snow has arrived but the crowds haven't, so get there quick to make your mark on some of the USA’s finest ski terrain.
Escape the cold weather to sunbathe on the beaches in Rio de Janeiro and ring in the New Year with a fun celebration on Copacabana Beach. And while you're near Copa, visit the neighborhood and beach that inspired the song, “The Girl from Ipanema.” Don’t overlook the other beaches, including Baixo Baby for families, Praia do Arpoador for surfers and Sao Conrado Beach if you want to leap from nearby peaks and go hang gliding.
You’ve got a pretty good budget so you can afford to go almost anywhere, assuming you are okay with renting one or two houses or villas instead of 4 hotel rooms. If you are willing to fly all the way to Asia, your best bets would be Bali or one of the Thai islands, probably Ko Samui or Phuket. In all of those places you should be able to rent a house or villa near the beach and then do activities and day trips very easily.
Really my first bit of advice is that the best place to get a really nice hotel that is on a beach or a hill and has the other nearby and also has great weather in December is Phuket, Thailand. You could go almost anywhere in southeast Asia in December and get good weather and low prices. But Phuket has over 1,000 hotels and hundreds of those are wonderful fairly luxurious hotels or villa complexes that could be perfect for a romantic honeymoon stay.
Keep Snacks Handy When You are Out – This was my snack stash for Disney World. I had Macadamia Nuts, Walnuts, Pecans, and low carb bars. I made sure to chill the water bottles in the freezer beforehand so that as they thawed throughout the day, we had cold water. When hunger hit, instead of falling to temptation, I just grabbed my bag of snacks before I got HANGRY. Doing so made it so much easier to make keto/low carb choices at mealtime. I kept my snacks simple because we already had enough to bring with us (if you have a baby and a toddler you know what I mean). I saw lots of people with small coolers who were snacking on fresh veggies and deli meats, but, again, my goal was easy breezy. You can find a great list of Keto/Low Carb Snack ideas here for inspiration if you prefer a variety.
Say Hydrated – This is a no-brainer and one of the most significant challenges for me. I never drink enough water, but it was hot this week in Florida when we were at Disney, and I could tell such a difference in how I felt when I was hydrated. I felt like it made it easier to stay strong and stick to eating low carb/keto as it helps to quench false hunger.
The Bali thing is also kind of a mess for those on low budgets. Kuta is a headache, and pretty much the opposite of what is so beautiful about the rest of the island, but it’s also where nearly all the really cheap beds are located. If you go a bit north in that same area into Legian and Seminyak, it’s nicer, but prices also go up. And Ubud is nice, but also more expensive for hotels and such. I’ll probably rent a place in Seminyak for a few weeks, which won’t be cheap.
While Cancun has become the king of the Mexican beach resort towns in the few decades since it was formed, it's only one of many, and all of them on both coasts have very nice weather in December. In fact, Cancun is probably the most expensive of them, so especially if you are coming from the west coast you are better off in Puerto Vallarta, Acapulco, or Los Cabos instead.
As for flight connections, Barcelona and Madrid should have decent connections to Toronto and Delhi, while Casablanca (Morocco’s largest airport) probably does not. So Spain is the better choice by that standard. On the other hand, you can get to Morocco by ferry from Spain in a short time, so you could go to Spain and also visit Morocco for a day or two.
If you really want to see the city up close, visit in November or December, when the crowds have dispersed. Hotel prices are comparatively low, and gondoliers are more appreciative of customers. And once you have your fill of religious art, head for the Peggy Guggenheim museum, which displays 20th-century American and European art in a home and garden setting. Note: October through January is the time of acqua alta, when Venice may flood. Usually it's not severe, and the city puts up wooden walkways for visitors and residents to traverse the water.
If an apartment isn’t your thing, or you have to book a hotel for your business trip, then there is one upside: the food. Typically hotels will include some sort of breakfast, and occasionally some sort of dinner plan. In Portland, we stayed at a great hotel that included both. Breakfast usually consists of pastries, waffles and oatmeal – but they almost always have eggs, bacon, and sausage ready to go on your plate.
Fortunately, it rarely rains at all in Cairo, so even though December is one of the wetter months, that means nothing and you are unlikely to see even a drop of rain. Hotel prices do reach their peak in Cairo starting late in December, so it's best to go early in the month if possible. Egypt is definitely one of the cheapest places to travel in December, and the weather is surprisingly nice as well.
You mention New Zealand and of course it’s summer there then, so it would be a good choice. However, all of these places will be crowded and near peak hotel rates if they are warm. So I’ll be happy to give you advice if you tell me if you’d rather visit one or more European cities in the cold season, or if you are looking for a warm place like New Zealand where it will be fairly crowded. By the way, the southern European cities such as Rome and Barcelona are lively and enjoyable that time of year, as the Christmas season goes on, and there aren’t too many tourists except for a few that travel to see their families around the holidays. So it can be a good time for southern Europe, as long as you don’t mind wearing a jacket or jumper during the day, and maybe a bit more in the evening. Give me a bit more guidance and I’ll be happy to try to help. -Roger