Nick, when you're at Universal don't miss "The Hulk", and "Revenge of The Mummy" - They are musts!
There are tons of other things to do. Here are just a few to get you started:
Busch Gardens - Tampa Fun Spot Action Park Old Town - Kissimmee The kids may find it a little dull, but there is the "Slingshot" that launches you 365ft into the air at 100mph, and the "SkyCoaster" which is a 130ft free fall in a hang-gliding sling harness.
Wet n' WildFantasy of Flight SkyVenture Indoor Skydiving
Titanic - The Experience I saw a smaller version when I was in Vegas - it was amazing.
Central Florida Zoo Gatorland Daytona Beach And here is an article about going to Florida with
‘tweens and teens.Also, I've had two bad experiences with Dollar Rent a Car down there, so I'd try to avoid them.