Firstly, let me just interject that JULY is no time for bringing small kids to sea world. It's just too danged hot for them. Even with the lagoon part...unless you plan on bringing a fan spritzer filled with ice water and keeping it on them continually, it's like walking through the Mojave.
Secondly, July 4th is going to be a MESS out there because it's a holiday. So be prepared for CROWDS.
Thirdly, do the waterpark FIRST! They will only hold so many at the waterpark and after they're full, they don't allow anyone else in until someone leaves...which could be eons. The waterpark is Fab for the wee ones. Better than at Hurricane Harbor because of the water levels (about 6 to 9 inches in the kids play area) but there's not allot of shade there so bring TONS of sun block.
I noticed a way for families to keep up with each other was matching tshirts. I believe a family went to Aeropostal and bought bright colored shirts, one made theirs or had them made and another simply ordered shirts off the internet so that it would be easy to spot a family member (the best shirts I saw were bright red shirts that read THING 1, THING 2, etc...so funny)
You are allowed to bring in a 6 pack cooler with you. I packed mine TIGHT with water and ice and brought a bag of extras for the day.
Renting a locker is $15 I think but you get a $5 coupon to use in the park somewhere.
Parking is $15 as well but you can get it on line for $13 sumthin which at least saves you some cash.
At Believe, sit close to the boxes that are places around the bleachers. They spray water on you periodically and will cool you and the kidlets off.
At Azul, DUCK, because the bird WILL fly close to your head. lol My daughter nearly got pegged by one.
The otter show is cute.
OH...you can rent a stroller On Line as well. I would check on line to see if they are available. They go quick. If there aren't any available on line, you WONT get one at the park when you get there.
I just got back last week and took our 3 yr old. He was exhausted by 2 and we got there at 10 that morning.
Hope this helps...
Hope you have a GREAT time!
Smiles to you and your family.