You don’t have to have a Group to be able to put a poll out on Facebook.
There’s various free tools that will let you put a poll together and share it, such as poll-maker.com and Easypolls.net.
You could have a series of polls in the lead up to the big event, where the winner is announced or features as a results. It could be for song choices, beer available, even favourite bible reading involving beer!
It’s a cheap and easy way to get people involved in the planning of the event and hopefully encourage them to come.