Dubstepped I think I would adore your family in real life!
Yeah, don't worry...churches rent out their halls all the time and seriously Episcopalians are lovely people. I've met a lot and haven't met a nasty one yet :). They probably aren't desperate for you to join their church and wouldn't expect it. I've been to many events at Episcopal churches, they are especially open to renting out their facilities.
My church gives outsider memorials and large group meetings non church related as well. There is a nice bee keepers monthly meeting for example. We are really friendly to these people but with no expectations. Don't be freaked out!