Open church reception

We are planning an open church ceremony and reception. Our church is maybe 60 people. I doubt half of them will come. We plan on inviting maybe another 50 people. It is going to be a late afternoon cake and punch reception. I have a couple questions.



1. What is the best way to extend the open invite? Put it in the bulletin, have our pastor announce it, send individual invitations to the members?
2. How many extra people would it be smart to plan for?