First off, I apologize for formatting. I'm posting from my phone.
I have been attending the same church my entire life. It is pretty small; there are probably about 60 to 70 people who attend Sunday morning service. For events that everyone is invited to birthdays, graduation parties, potlucks, baby showers, etc. they are announced from the pulpit for a few weeks prior and an official invitation is posted on the bulletin board in the lobby for everyone to see.
Most of the members are an older generation, meaning that I have only seen one wedding at my church ever. This was announced and posted the same way. There was no way to RSVP for that event.
It's been accepted that my invitation will follow the same pattern. I know it's not very formal, but it's the way things are done. I am also inviting everyone to the reception. It's not going to be a very formal event think church potluck held in a community center, although all food will be provided the guests will not need to bring anything, so I don't need an exact head count or even specific names for a seating chart but I would like to have an approximate number for how many plan to attend.
I was thinking about posting a sign up sheet by the invitation name and how many attending. Again, I think it fits the formality of the event but I don't know if it's appropriate since this is a wedding. I was wondering if anyone else had a similar situation and your opinions or solutions.
Just as a note: I really don't want to do individual invitations. For numerous reasons: Cost, Some children come to church with there grandparents but they don't live together and I don't want to worry about who to send things to, if new members join the church I want them to feel welcome but I don't want to have a constantly revolving guest list, etc.