We stayed at Treasure Island resort and it was fabulous. 3 pools, games, activities. Next door to a big shopping centre so we self catered most of the time.
Personally I wouldn't stay in Surfers, not geared towards families.
This - while not on the beach, it is geared towards kids.
I would go to whitewater world with your age children over wet n wild, I find the majority of the rides are geared at the 12+ age group, and it is an older age group that attend vs the families that go to white water world.
If being on a beach is important, look at the Gold Coast Tourist Parks website, you may be able to get a cabin. The kids have a ball in these situations - very social.
Surfers really is not a nice place these days unfortunately. We have stayed at the Paradise Resort, and that was ok, not 4* by any means, but a bit further out of the main part of surfers.
Being away from the action sometimes is better with kids.