You could consider cancelling your transfers (at least back) and renting a car.
A 5 pm flight could give you a few hours at Blizzard Beach or Disney Quest. It could let you see Kennedy Space Center. If you are a WDW AP holder, it might even be worth a trip into the parks (I don't think it would be unless you already had an AP). You could have a late breakfast at Chef Mickey's, then resort hop. Or visit DTD. You could explore the Orlando outlet mall.
But to do this, you'll want a car. Then your luggage can go in the trunk (or check it getting off the ship - depending on who you are flying with).