Florida for sure. I grew up there. There's a ton of options for the kids. Great fishing both salt and fresh. I'm headed that way in a few weeks. You can get some good rates too if you do some research. Have fun.
Go straight to the Florida Keys. Do not pass Go, do not stop anywhere along the way. Warm. Overflowing with fish. Plenty of things to see and do, mostly fishing related! Big fish, small fish, shallow fish, deep fish, sharks, . . .