I’m happy to hear that this information is helpful. My first thought is to wonder if you’ve been to Goa yet? I’ve spent 4 total months in India to about 15 different places, and I know all about the insane crowds and whatnot that you would prefer to avoid. In my experience, Goa is totally different, and that’s where I’ve spent by far the most time. I remember spending time on Calungute Beach and I was surrounded by mostly domestic Indian visitors including many families. There are other beach towns and areas that are even more mellow in the south. The beaches there are quite nice as well, which is something I didn’t find as much of in Kerala, Putacherry, or even Puri. At least it would be the fastest and most affordable destination, and it should be very nice in December.
Southeast Asia is easier to deal with, and there are cheap flights connecting in the Middle East and landing in Bangkok, Kuala Lumpur, and Singapore. Each of those is a very interesting city, and there are many smaller places to go in the same region. In Malaysia there is Penang and Melaka. In Thailand there is Chiang Mai and quite a few others in that area. In Laos you can visit Luang Prabang, which sounds like it could be a winner for you. And there is also Siem Reap, which is home to the amazing Angkor Wat temple complex.