HI Lydia!  Your trip will be here soon!  How exciting!
My family always does mini-golf at least once per trip.  The Fantasia Gardens course is definitely a better option for adults as it is a little more challenging than the Winter Summerland course.  They are both a lot of fun though, and we have never been to either one when there was a crowd. 
I would also recommend that you check out Downtown Disney.  It's a great way to spend time outside of the parks.  There are lots of shops and restaurants.  You can also catch a movie at the AMC theaters, or see a Cirque du Soleil show, La Nouba,  that is exclusive to Disney.  I have seen many Cirque shows and it is by far my favorite one!
My husband and I also like to spend time on Disney's Boardwalk.  It's great for strolling around, eating and catching some entertainment along the way.  We also love going to Jellyrolls when we are there on a trip without our children.  It is a dueling piano bar.  It's a great place to hang out, listen to music, and even get up and dance a little!
I hope this helps!  Let me know if you have any other questions before your trip.  Have a magical time!!!