We just got back from Treasure Island (it's right before St Pete Beach) in July. I think Maderia Beach or Indian Shores would be a good place to stay. I thought the beach at TI was way too wide. Also, if we ever go again, I would definantly get a condo facing the ocean. Most of the motels didn't have a lot of ocean front rooms and I really missed that.
We ate at several good restaurants. One was PJ's, it was seafood. Also, there was Dockside Dave's--very casual, but great food. Another place we enjoyed was Captain Kosmakos. It was a nice restaurant, but not super fancy that you couldn't take kids. They had huge portions there!!
Also, if you have kids, try the Pirate Cruise in the evening. The one at Johns Pass was good, but I think I would go for the one at the Clearwater Pier. Be sure to check that area out in the evenings. They have a lot going on 2 hours before and after sunset. Oh- if the Pirate Cruise isn't your thing, try one of the dolphin sighting cruises.
And if you go to Honeymoon Island and go on a nature trail....BEWARE OF MOSEQUTOES!!!!!!!!!!!!!!!!!!!! Especially if they have a sign up about them. We were not prepared for the extent of them and got ate up!!!!!!! DD ended up w/ 250+ bites!!!