How about staying at Universal for those few nights? You can get connecting rooms, and probably the best benefit, is the front of the line pass that comes with it. In many cases, you will be almost to almost walk on every ride (excluding Harry Potter). If I wanted to go to Universal, I would consider the cost of the room a small price to pay for not standing in line.

I know that doesn't help with going to the Kennedy Space Center, but you might want to also consider it for 2 of the 3 nights, since that front of the line access lasts until midnight of the day you check out.