We're in Fredericksburg now. Did this yesterday and can strongly recommend it.
Bring lots of water! Climbs are not hard, just pleasantly rolling mostly. Stop at Harry's for a beer at the end of the Willow City Loop. It looks like a biker bar but.. well it is. But you can sit outside:
http://www.bikely.com/maps/bike-path/Willow-City-Loop
Our friend is praying for rain (it's a bit dry now, but it should be in bloom when you get here).