If you are staying at the Doubletree, which is just outside the Universal theme park, then can I make a radical suggestion.
Dont even visit any of the Disney parks and base yourself round the Universal parks.
Universal have a deal with Wet and Wild (water park) and Sea World for combined tickets. These tend to be better value than the Disney tickets and the four parks are excellent.
Universal have 2 parks - Universal Studio and Islands of Adventure and both are great parks and are on your doorstep.
Wet and Wild is only half a mile away so is within walking distance. and Sea World is 6 miles so may need a bus or taxi.
If you are there for a week there is plenty to do in those 4 parks to keep you busy. We spent two days in Islands of Adventure and two days in Sea World and still did not see it all.
Ticket options here:
http://www.universalorlando.co.uk/tickets.html
I would go for the NEW - Orlando Flex Ticket (dont both with Busch gardens as it is about 50 miles away)