I am a catholic and a musician, and (believe it or not) a volunteer communion minister. I don't really see a problem here. If a mass is scheduled let those who wish attend, others can join them after the mass. If however the event is threatened unless all attend the mass then I say screw that and go somewhere else. I do know that non-catholics are always welcome to attend mass as I am welcomed at other non-catholic services. If one does not want to receive communion that is ok as well. Many catholics do not always receive the sacrament, some will however approach the priest or the server with hands folded across their chest as a sign that they only require a blessing and not communion, others just stay in their seats. I would schedule the event with a timetable, listing all parts. e.g. Breakfast 8.00am to 9.00am, Mass 9.00am - 9.30 amm. Welcome remarks etc 9.45am and so on. No one should be forced to attend mass and/or no one should be made to feel excluded. The idea of having non-catholic services listed is a good idea and a valid suggestion. Remember, you don't always need money to promote music, a small room or a kitchen where people can gather is all that is required, funding can always be found if needed.
Play it - they will come.

Slan.