My experience is travelling without children, but I’ve seen people with children of all ages in all of the below countries, including in deep caves (a bit extreme in my view), on snorkeling trips etc. I was amazed by how comfortable and happy the children were even when not in places with water slides and…whatever else children need on holiday :)) :
Thailand - is popular for a reason. It’s cheap (esp if you don’t mine eating in local restaurants etc) and safe. I went there several times, we hired a car last time and travelled throughout Thailand. Without a car you can do a few days in Bangkok (it’s easy to use public transport once you get the hang of it) and then fly to one of the islands. The north is ok but only if you want to hike to remote villages etc, which may be hard with children. The more popular islands are more expensive. I went to Koh Lanta last winter, glorious. The entire 3 weeks holiday, car hire, food and accomodation came to £2,000 per person based on 2 sharing (including a little resort right on the beach).
Vietnam is perhaps even cheaper and really interesting (if you like visiting floating villages etc so nothing fancy) but more difficult to get from north to south unless you fly.
Philippines is my favourite because i love island hopping, lots of snorkeling, anything on and in water (especially in the Palawan area). Glorious rice terraces up north but not green in the winter.
Sri Lanka is also very nice, the area where the tea plantations are is so beautiful. There’s a train journey in that area which is stunningly beautiful. Saw elephants on the road, monkeys stealing our breakfast in the little ‘jungle’ place we stayed in, peacocks everywhere. I still remember eating an icecream at a small temple and seeing, with the corner of my eye, how the monkeys gathered above me, closer and closer. I genuinely felt like pray being stalked by predators 😀. I wisely handed my icecream to one of the monkeys who proceeded to lick it just like us humans do. Or monkeys begging from humans with their little ‘hands’ cupped just like human beggars and making little noises. Adorable and a bit disturbing in equal measures.
Cambodia is worth going to if you want to see Angkor wat, but I think it may be a bit too hot and exhausting for small children.
Myanmar- hmm, lots (too many) temples to visit but maybe not for small children.
In comparison, I found South America more expensive, felt a little bit less safe (perhaps I just prefer the Asian culture more), I didn’t enjoy the food as much. Mentioning this is another location where it’s HOT in the winter.
Check where is the right season - wet/ dry
im off to Borneo this winter, can’t wait!