Vietnam might be your best choice of the three. Most people (if they can) fly into Hanoi and fly out of Ho Chi Minh City (Saigon) or the other way around. Again, you can travel between them by train, although getting tickets can be a bit complicated. Hanoi is really interesting and nice (and super cheap). The best tourist city in Vietnam is Hoi An, which is between the two big cities. There’s a nice beach there and a bit farther away is Denang, which has large resorts along an excellent beach. Nha Trang is another good beach city in Vietnam, but probably not great for families. Ho Chi Minh City is bigger and more crowded than Saigon, but it’s also more modern (and hotter). You could spend two really nice weeks going north to south in Vietnam with a long stop in Hoi An.
December might be the only month of the year in the Canary Islands where very few people would consider sunbathing. Still, compared to everywhere else in Europe, Tenerife is balmy. The largest and most English-speaking of the Canary Islands, Tenerife is no mystery to the hundreds of thousands of northern Europeans who spend a month or more here every year.
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.
If you are looking for an island that is moderately priced in late November I would probably head to Thailand. The rainy season typically ends in the middle of November in Phuket and Ko Samui and the other popular islands, although you might still get a few quick storms in late November. One nice thing is the crowds don’t start coming until mid December so you have a huge selection of hotels at really good prices.
Being from Mumbai you can be forgiven for not realizing how unappealing beach areas are when the air temperatures are only a bit above freezing. Seriously, even beach on the European mainland is totally deserted by November 1, and many of the local hotels and restaurants are closed by then until April or so. Now, if you are mainly after the novelty of being on a beach in the European winter, you can certainly go and still find open hotels and restaurants. If I had to recommend one place to consider it would be Spain’s Costa del Sol, which is the resort area around Malaga. The average high in December in Malaga is 17, and the average low is 8. You’d be the only one on the beach, which might be kind of nice. It’ll also probably be windy. If you were going to do that I’d recommend staying in Malaga itself, which does have a nice beach area in the city, and since it’s a city the hotels and restaurants will all be going.
Actually, most of the popular European cities have fairly mild winters, in that they don’t spend much time below freezing and snowstorms are rare as well. It’s hard to make suggestions without knowing about your tastes, but I will tell you that the most popular European cities are London, Paris, and Rome, and none of them get snowed in often. If you are going to Italy, you should also go to Florence and maybe Venice as well.
December is a popular month to go cruising around Hawaii and Mexico. It’s an ideal family trip, especially with most kids in the US out of school for the holidays. Experience the Hawaii’s tropical paradise. Pick a popular cruise liner and visit ports of call like Nawiliwili on Kauai, Honolulu on Oahu and Kona on the Big Island. If the Caribbean floats your boat, we recommend taking a cruise to explore Mexico’s Costa Maya, Cozumel, Ensenada, Acapulco, Cabo San Lucas, Puerto Vallarta and more.
If the Caribbean sounds better, I’ll recommend Puerto Rico. The area around San Juan is fairly crowded, although not nearly as crowded as a typical resort area that is loaded with hotels. And there are many smaller resort towns on other parts of the island where people usually rent a condo for a week or two. In a town like Rincon you won’t get crowds, and you will get great beaches.
My other two suggestions are San Juan, Puerto Rico and Cartagena, Colombia. Both cities have really wonderful colonial districts and modern resort districts nearby. San Juan is more expensive, but still reasonable, and it has far better beaches. Both have a bit of rain in November, but it tends to come and go quickly. You’ll get similar rainstorms in most of the Caribbean in November, so it’s a bit tricky. I hope this helps. If you had something else in mind let me know and I’ll try again. -Roger