When I attend a Roman Catholic Mass, and I am acquianted with the priest, so that he knows I'm an evangelical, I go up with the others, and recieve the blessing, rather than the eucharist (which would be violating canon law). I have no problem with that at all.

Most of the western musical tradition has to do with the Mass. That is just how it is. Those that aren't actual works for the Mass are significantly influenced from the music of the Church used for the Mass.

In that context, I don't see a problem with having the Mass at your event. Just be sensitive, make sure all know the rules about the eucharist and the blessing, and with the priest's consent, perform appropriate musical pieces that intersect between your groups' focus and the Mass. That way, not only with Catholics recieve spiritual nourishment, but non-Catholics will have an educational experience.

Steve