Well, you could have a nice leisurely lunch at any of the resort restaurants along the monorail that serve lunch. I would suggest Kona Cafe, of the Grand Floridian Cafe.
You could hop on the monorail, and spend 1 1/2 child free hours in the MK.
If you have a car, you could go to DTD or some of the other resorts.
You could do what we did... go to the different resorts and collect the smashed pennies... that is how we saw CBR, CSR and the AS resorts. A car really is necessary, though!
You could rent the water mice at the Grand Floridian and take them out on the Seven Seas Lagoon.
You could get a cocktail and sit by the pool or on the beach, and enjoy each other's company.
There are a lot of options, take advantage of them!