Sometimes it rains or it is just to hot outside, so you have to look indoors for some fun things to do. Obviously, The Citrus Park Mall is going to be a good choice for people of any age, because there is something for everyone. The mall has a good selection of restaurants in or near it, there is a movie theater and some kid play areas. If the mall is too fancy for you head over to the Oldsmar Flea Market for a fancy good time, rain or shine.
If you like to gamble, the horses will run in the rain or you can play poker at Tampa Bay Downs. Check the schedule before you go to make sure that there is live racing, but if you haven't been in a while Tampa Bay Downs can be quite entertaining and you don't have to gamble a lot to enjoy it. Unfortunately, this part of the county does not have a ton of indoor activities available, but the other parts of the county do.
If you are trying to entertain children do not despair, there are some good options for burning off their energy, even if you have to stay indoors. The Jump Zone is one option and Gator Fred's is another. Both of them will keep your kids busy all day, so long as they are big enough to enjoy bounce houses. PK Playzone is a giant indoor play area and restaurant that could salvage a rainy day for you and your kids.
You could always just try one the restaurants that you have been meaning to and catch a movie.