There was a similar question here about 9 months ago regarding Bali. You might find the answer helpful. http://answers.worldnomads.com/questions/indonesia/1260/best-place-to-sray-in-bali-with-a-2-year-old
Kids can be particularly susceptible to some of the tropical diseases (they dont get hygiene!) so take some antiseptic wipes. make sure they wash their hands every time before eating food.
They'll want to run around in shorts and t-shirts, which leaves a lot of skin exposed to mosquito bite. Try to keep them in long sleeves and slather them in insect repellent (Dengue Fever is a big problem and the mosquito is active during the day).
Take a gastro' kit.... if kids get sick it can get serious very quickly and rehydration is the key.
If they're very young (infants) they may not have had all the routine vaccinations we take for granted, so check with a doctor 6 to 8 weeks before your departure to discuss your options.
Take precautions, it'll give you peace of mind. SE Asia is a great destination for kids, you'll have a ball! almost 8 years ago
I'm not sure about SE Asia, but have you considered Fiji? There are some great family friendly resorts both on the main island and on some of the outer islands. The staff are amazing and love entertaining the kids if they are being boistrous during meals. Cheap child care and kids clubs and you can choose to relax on the beach or go exploring, snorkeling, fishing, island walks, inter-island trips and heaps of other activities. I stayed on Plantation Island last time I was there and it was fantastic! I guess it all depands on the age of the kids and what you are looking to do on your holiday. almost 8 years ago