The Void at DS is a star wars or wreck it ralph immersive video game experience, there are two mini golf courses; rent the water sprites at one of the resorts.
An afternoon early evening at Animal Kingdom Lodge is great fun, you can not use the pool of course but they have a kids activity "trail" earning beads for each completed section, lots of animal viewing, storytelling by the firepit at sunset, and night viewing of the animals with night vision goggles.
You could do a character meal at one of the resorts or head to the boardwalk for carnival games, an ice cream at Ample Hills (best ever!) and then catch illuminations from the bridge. Monorail ride with a stop at each resort for a snack and maybe a trip to the arcade.
Ft wilderness campground has several activities and an evening singalong campfire - the camping forum here will have more details.
Don't forget that adding extra days to a 4/5 day ticket becomes very affordable, if you think the two of you may want to hit the parks again just upgrade prior to the end of your last day to get the discount.
Have Fun!