As part of the planning for the Texas Hill Country ride, the spousal unit and myself spent a few days in Fredericksburg in the spring. We found a lot to do there - it's not just riding the hill country that attracts people to this town! Here's a few ideas for Sunday or those who may not want to go on the planned rides.
For history buffs - the National Museum of the Pacific War is here. This is, next to the Smithsonian, one of the most incredible museums I've ever seen regarding World War II. It has 3 parts and takes a full day to go thru, but if you just want the best stuff, go to the George HW Bush Gallery for the interactive tour and incredible exhibits. Expect to take 3-4 hours for this alone.
http://www.pacificwarmuseum.org/If you want to listen to music and have fun, there are multiple bars for such. But we went to a place called Rockbox. It's a theatre with impersonators. We loved the music and it was a lot of fun - great comedy goes on as well.
http://www.rockboxtheater.com/Of course, there are also multiple vineyards situated in the area and we tried to but could not find a bad wine in the bunch. Being that you'll be riding, you might want to taste a little less than usual before purchasing and taking a special reminder bottle home with you. (maybe we should do that instead of a t-shirt next time)
http://www.fredericksburg-texas.com/WineriesVineyardsRM