Thailand is great for kids, my first backpacking trip with my daughter she was 8 and we did the Northern part of Thailand. She had an absolute blast, the Thai people love kids and we felt welcome wherever we went.
We ended up "lost" in a smaller town during Loi Krathong and wandered a temple during the evening watching everyone buy and release their krathong.
A family waved us over and shared coffee and snacks with us on blankets til it was dark, their daughters braided my daughter's hair and mine taught them to play rock paper scissors since it transcended language barriers.
Our trip to Thailand was one of my very favorite memories. :)Okay, so I don't have kids yet, but I was a kid and a teen and am now an adult.
The kinds of trips my friends and I would take, or my husband and I have taken... are so, so vastly different from the experiences I had when I was younger.
As a kid it was a lot of camping, sight seeing, going to specifically family friendly places like DisneyWorld. A lot of it was visiting family and then taking time while out there to go do fun things.
When I was single with my friends? It's MTV's spring break and we're bringing down the house. There should be NO children there at all.
Trips with my husband? We're going wine tasting, then bringing a bottle back to the hotel room, getting trashed, and engaging in some marital activities. The first part would be boring and a waste of money for kids, you'd have to mind them instead of doing what you want to do, and then you'd need to have two separate but connected rooms (or a suite) for some privacy and still have the same issues of your kids getting in the way of your marriage.
There is a big difference between family trips and adult trips. A lot of places, like Disney, even account for that and have kids day clubs and babysitting in the hotels. Hell, that's why cruises are so popular, the kids can wander about free range or hang out in the kids clubs and the adults can go have some free time. But if you're not in a position where you can do something like that, then you really need to figure out what the purpose of the trip is and stick to it. Maybe alternate between the types. Otherwise, everybody is gonna be unhappy