It will be quite crowded in July but it would make for a great weekday morning. If you get there at opening you shoulld have time to try everything at least once. I would recommend Blizzard beach for 11 and 13 if they enjoy thrill rides, the slides are higher and faster. If they aren't into the thrill rides Typhoon Lagoon has a better wave pool and the water coasters are fun but the rest of the slides are nothing compared to BB. Blizard Beach is across from Animal Kingdom. It should be about a 15 minute bus ride. If you have a car parking at all water parks is free. I would plan to leave the water park after lunch and make sure you use plenty of sunscreen and keep reappling.
Also on your way in purchase a refillable mug. You can refill it as often as you like throughout the park. If you have so much fun you decide to go again, you can purchase a new sticker for less than the original mug. The mugs are interchangable between the water park.
I don't remember wet and wild but I went to the water park near Bush Gardens last year and while there is more picnic room and shade at the others the slides and such were better at Disney's in my opinion.
When I go up with high schoolers the love to spend a day at BB.