Sounds like you're off to a great start! Love the monthly challenge idea. One suggestion I have is to make sure you have enough space for each person. I like to work on my own folding table (I think it's a 3x5ft) and when I have one here at my house I put all the tools on a separate table a little off to the side and sometimes in an adjoining room so we're not too cramped.
We always bring a dish and do kind of a potluck and of course m&m's are a given.
Hope you have a great crop!