What type of pass do you have? Annual pass? If it was an AP I wouldn't think twice about spending 3 or 4 hours in the park before leaving, but if I were buying the days w/my package or for my trip it would depend on the $$ difference for that extra day. I have a hard time burning a day (we usually have a 10 day no exp. tix that we work thorugh then get another) for only a few hours. I like to save those days for a fuller day at the park.
If you don't do the park, DTD is a great idea. Or, depending on your resort you could hang out & enjoy the pool (some of them have hanging rooms you can use if you've checked out or arrange for a late checkout). Maybe try one of the mini-golfs? Or head over to the boardwalk to enjoy the stores, restaurants, ride the boat, rent a bike, etc. Ft. Wilderness has the petting zoo and some other activities too.