I am going to say what you don't want to hear, and what you probably already know: You're probably not going to enjoy it and will not want to get into cross IMO. 28's are a far cry from 35's or 38's. I roll on 700x32's and I can tell you that it is much more jarring than I would like. I couldn't even imagine riding on 28's... nevermind on a CAAD3, which to me is one of the most uncomfortable modern road frames ever created. It's ok as a crit bike I guess, but cross? On 700x28's??? No way IMO.
Find yourself an old touring frame an go from there...