Being serious, don't go to pattaya because it is a dump and pretty much the only thing there is bars as greenietea said.
I've been to hua hin a couple of times and it's very nice, perfect for families and be sure to go up the mountain at the south end of the town and visit the shrine and feed the monkeys. You're a braver person than me daring to drive in Thailand though
I'd also recommend Ko Samui, you can fly direct from HK and miss out Bangkok altogether which must be a bonus, and it's got some very nice beaches. If you want quiet it's probably better to stay away from Lamai or in particular Chaweng, although Chaweng noi beach is quieter. Imagine most of the 5 star hotels are in the chaweng area though because it's most popular. Avoid Ko Phanghan unless you like dirty backpackers bragging about how little they are paying for their bungalows and sampling Thai culture whilst never actually talking to anyone who isn't from a western country