Hi Gary,
I think there are definitely more than enough rides to fill up 3 days. Moab tends to lend itself to a little more open riding than single track since it is a desert area. The riding is incredible!
I would suggest looking at some of the guides for the Moab area at this site and maybe picking up a trail guide at the visitors center when you get into town on Main Street. Here's the Motoutah site.
http://www.motoutah.com/content/category/5/37/38/Chris