Thai website for kids to learn Thai

Sorry can't help you, but if you don't get any answers here you could try posting on one of the many Thai forums...like pantip.com

How old are the kids? If they're teenagers they could use one of the many free Thai language websites, younger than that....sorry I can't help either!

Another very useful resource is the Women Learning Thai website

http://womenlearnthai.com/

but it does depend on how old your kids are!