I'm teaching in Thailand. Not at a really top school but a decent one. We don't get accommodation costs but the top schools will contribute towards this. Health insurance is a no-brainer, I really wouldn't work at a school that didn't offer this for me and all dependents. Ours includes US but if you're coming from the UK, it's still an adjustment to have to pay anything at all, for example childhood vaccinations are not covered by my insurer.
Rayong is a nice area, you can spend weekends at the beach or even on an island. Will your other half be working too? There are lots of teachers here with a non-working spouse, but for us it wouldn't be worth it at all if my husband didn't work too (he's not a teacher but he managed to get a job for a Thai firm before we arrived... this is difficult to dp).
Eating out is cheap. There are international supermarkets where you can buy western brands but obviously at a premium. We've found ourselves eating a lot more chicken than we used to and a LOT of rice! We have found everywhere extremely child-friendly (I have a 4 yr old and an 18 month old). But not buggy-friendly! I wore my son when he was small and then he had to get on with walking!!!
Most half-decent schools will cover 2 child's places for a teacher. Again, without this you would struggle as you can't put then in a government school and international schools are not cheap! It helps with the diversity of the student body anyway, as many schools here cater for quite a lot of rich Thai students and welcome more foreigners. Also, the market is pretty saturated so there will likely be places available.
It's normal and affordable to have home help. We have a full time nanny for my son and can't imagine going without now! I will keep her even when he starts school, as she can do the school run and allow me to stay a bit later at work. Most people with children have at least a bit of help at home.
Your salary will likely be taxed, and you are unlikely to get a pension contribution, but most decent schools will make this up by giving you a bonus every year (maybe every second year) of a month or two extra salary. This may or may not be taxed, depends on the school. You're supposed to use this as a pension contribution of some sort (invest it or pay it into a private pension) but of course you can do what you like with it.
We also get flights annually, which is great as some schools do every other year. We get a cash equivalent of BA/Thai Air flights to London every May. Not going home this year so that is just extra money for us, and as a family of 4 it will be quite a chunk of money!
If you have any more questions, please ask. And if you want to discuss the specific school feel free to PM. Overall we're having a v positive experience! We could earn a lot more money in other locations and we're open to that in a few years, but for now we're very happy.