There's TONS to do without ever leaving the Wilderness Lodge! You could enjoy the pool and hot tubs. You could rent Water Mice boats and zip around the lake or rent bikes and ride the trail over to Fort Wilderness to check out the stables, petting zoo, etc. There are always scheduled activities going on in the afternoons at the Wilderness Lodge - volleyball games, pool games, arts and crafts sessions, WL tours, etc. You could play checkers in the Iorn Spike room at the villas, or just spend some time exploring the amazing resort and grounds. You could have a fun dinner that night at Whispering Canyon Cafe or a romantic one at Artist Point. The Wilderness Lodge is such an amazing resort! I definately reccomend that you take some "down time" during your trip to enjoy all that it has to offer.
If you want to leave the WL, you could head to Downtown Disney or the Boardwalk for shopping and dinner - and maybe even drinks and dancing if you don't have kids with you.
You could take the boat to the Magic Kingdom and then hop on the monorail to explore the Polynesain, Grand Floridian, and Comtemporary. You could check out those resorts and have dinner someplace like Ohana or Chef Mickey's.
You could play miniature golf at Fantasia Gardens or Winter/Summerland. This is really a lot of fun and it's something we do on every trip!
If you want to venture off-site (if you have a car) you could head to the outlet malls or over to Celebration for shopping and dinner.
Hope that gives you some ideas!