I don't know about July, but we did spend last August in Disney. While it was very hot and humid, it wasn't so bad because alot of the rides are indoors and a/c. There's always the FastPass option you can use if you purchase the Hopper tickets.
As for other things to do: There's the Serpentarium in Orlando or maybe it was Kissimmee? The girls loved it! We got to watch them milk poisonous snakes. A few weeks ago we were watching Animal Planet and it was the same guy on there...turns out he's one of only FOUR people in the entire country that does this for research/medical purposes.
There's also what used to be known as Old Towne. Can't remember the new name of it, but they have go-cart tracks and other rides and shops. If you google it, you should be able to find it.
The T-Rex Cafe at Downtown Disney is AWESOME! There's animatronic dinosaurs and all kinds of things.
If you have any questions, feel free to PM me and I'll give you a bit more info.