If you are very sensitive to humidity (I normally am, to be honest) then you’ll find more pleasant weather pretty much anywhere else in Southeast Asia in December. It can actually be cool at night in places like Chiang Mai that month. On the other hand, I LOVE Bali and I’ll probably spend all of next February there, which is still in the wet season. I’d still seriously think about Bali if I were you.
Actually, all of my best suggestions for those things are in the article above. One challenge you’ll have is that all popular tropical destinations have their peak weeks at the end of December because so many people in cold areas have that time off. So flights to Central or South America are going to be fairly expensive, although buying soon can help. For hiking and views I think Costa Rica could be a good choice, or Nicaragua. You could also go to Bariloche in Argentina, though it’s probably not worth going all that way unless you were also going to spend some time in Buenos Aires and such.
Rio is probably the most beautiful city in the world as far as the setting is concerned, but it’s also famous for petty crime. As you mentioned, I think it’s quite easy to stay safe as long as you are aware of the situation. The biggest problem by far is tourists getting robbed by someone holding a knife or sometimes a gun, and they are often in groups. However, this almost always happens to people who are walking close to the water on the beaches after the crowds have gone for the day. The sidewalks along Copacabana and Ipanema are brightly lit and safe, but there is a mound of sand between the sidewalk and the water, so if you go to the water you can’t be seen by the security guards and police on the street. As long as you avoid that, and any other situation where you are alone in a dark place late at night, you’ll be fine.
The park we visited has an app you can download on your phone that allows you to reserve a table at any table service restaurant on their property ahead of time. The app also lists the daily breakfast, lunch, and dinner offerings at every single food establishment on site. There really is no excuse for settling for the popcorn or french fries when you can easily find a place with compliant options if you’re willing to look and tweak a bit. A lot of other theme parks are either offering similar apps or putting their information online for those who need to research their options ahead of time. If your destination is the beach or a famous city, check out what’s in the area online, or call your hotel to get an idea.
Sri Lanka could also be great, and it’s very different. In fact, you might even consider a trip to India itself, which is obviously similar to Sri Lanka. But Sri Lanka is far easier to do in about 12 days, with most of your time spent in the mountains and a bit along the southern coast. Colombo is mainly just good for flying in and getting your bearings. Sri Lanka is also a bit more expensive than Vietnam, but both are great value. And again, you could instead go to Kerala and Goa in India on a short trip, although those are more about relaxation than culture. Let me know if you have any other questions, and I hope this helps. -Roger
And if you are mostly interested in adventure and nature rather than cities, you might also consider India. The cities in India are complete insane asylums, but once you get outside of them it’s a beautiful country. The area of Kerala and its backwaters are a big highlight. They’ll remind you a bit of Sri Lanka in some ways, although things are cheaper and the scenery is quite different. The various beach areas of Goa, just to the north of Kerala, are also worth considering.
Overall this is a perfect time of year to visit almost anywhere in Argentina. When December arrives things really start filling up and all the locals are on their own holidays, so November is the ideal mix of great weather that isn't too steamy, and modest crowds and prices. With Argentina's recent inflation and currency devaluation, it can be hard to know how expensive this trip will be, but for most people it will be cheaper than in recent years.
Two of the easier other choices would be London or Madrid. From Amsterdam you can take a train to Brussels and then change for the Eurostar train to London, or you can fly. From London to Barcelona you’d want to fly for sure. If you chose Madrid you can go to Amsterdam and then fly to Barcelona and then take a train from Barcelona to Madrid in only 2.5 hours.
Without knowing more about your interests, my top suggestion would be to focus on Sydney and Melbourne and the areas around both. The Blue Mountains near Sydney are also nice for a couple days or so. The main challenge you’d have in seeing a lot of Australia is that it’s all so spread out. You can hire a car for Melbourne and Sydney and that whole area, but it’s better to fly to get to Uluru (near Alice Springs) or Brisbane or Cairns/Great Barrier Reef or Perth. You’d be driving for days in between those places if you started from the southeast area where most people live.
Every year it goes the same way. My mom calls me up a few weeks before Thanksgiving and asks me, “You are bringing green bean Casserole this year, right?” before she launches into a chorus of “You have to! No one else makes it just like you do!” Green beans have become “my thing” around the Thanksgiving holiday, and it’s the dish that I am expected to bring to dinner each year.
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.
Since you mention the temperature in Fahrenheit, I’ll assume you are in the United States. You might have to go to the Southern Hemisphere to reliably get 84F or higher, but you can get over 80F in most of the Caribbean. You’ll get low 80s in Hawaii in early December as well. Fortunately, neither of those places get too crowded until just before Christmas, so either should work.
If you’re a bit more on the timid side, you can always use Yelp and TripAdvisor to get good insights on places people have visited. As a disclaimer, some of the ratings may not be accurate on these sites, so make sure you go through and read some of the more recent reviews that people have written. We did this for a few of the places we visited and had no issues.