Wow, that's a LONG road trip! Disney World is just the best!
That's where I took all my family vacations as a kid!
It will be very hot (and yet amazingly it will get a LOT hotter the closer to August you get!). My best tips/suggestions: keep hydrated! I know they're checking bags when you enter the parks though I'm not exactly sure what's allowed and not. If water bottles are then take some, if not, just take EMPTY bottles and fill them up there! (And of course bring snacks! They charge an arm and a leg for snacks!)
They also offer something called Fast Pass, which you scan your ticket and at the designated time (it gives you a ticket with a time on it) it lets you skip most of the lines!
So you can pick where you really want to go and if the lines are crazy you can use that and do something else in between!
Above all else:
HAVE FUN! 