Bangkok is a wonderful hellhole, you have to see it once though, just to say that you've been there. I stayed in Phuket twice, it's very idyllic in some resorts, not so much in others, do your homework before you go. Patong is very brash and so is Karon, though on a smaller scale, I stayed in Kata Noi which was gorgeous, just the right mix of everything for a family, I also stayed in Cape Panwa, also highly recommended. Hua Hin on the mainland is great and the restaurants are fab, but you have to hunt out some decent beaches, they are there apparently.
What are you looking for out of the holiday?
Pattaya has a certain reputation but I understand that they are trying to appeal to a wider audience of tourists.