Check the rental car rates and compare to the cost of airport transportation. I can usually get a car from National for about $120 for a week (Emerald Aisle, Disney Club discount, 1 free day coupon). Tiffany Town Car from the airport is about $90 with tips, so it's not much more. That way you would have the car for Universal, grocery shopping, outlets. I would also drive to AK, the bus is a long ride that usually stops at Blizzard Beach. Also drive to Downtown Disney & Pleasure Island, bus waits can be long there.