Often what intimidates reluctant 'racers' is the worry of flying a spinnaker
, or the worry of not having a spinnaker
(or knowing/wanting to use one) etc.. For that group a 'non flying sails' division keeps things simple, and you'll often get more professed cruisers willing to take part. Providing them a separate start (the other major intimidating feature of 'racing') helps too. The Pursuit style makes things a lot more fun for the slow boats, as mentioned already.
We've also, in the past, put 'better' sailors on other boats to speed them up and get them a taste of being in the thick of it. Lots of learning to go around, and finally a casual debriefing at the end of the day, a few suds and discussions about what he/she shoulda coulda done in that situation is always a lot of fun, adds to the social dimension and makes for closer friendships among the 'competitors'..