Our town seems to be lucky, because this is one thing we NEVER have problems getting volunteers for!
Personally, I think EVERY mom should be included, because every mom that wants to be in the classroom with her kid shouldn't be denied. There should be one "class mom" who's the organizer that makes sure everyone else gets turns during the year to be with the kids.
I gotta toot my own horn here. When I managed to get the honored position when my son was in kindergarten, I was so paranoid that people would think I was being selfish, that I made a little chart of all the mom(or dads) with their phone numbers, and any scheduled events (unscheduled ones I added in as I went along).I checked off on a little box which parents participated in what activity, so that way I didn't lose track. Parents that weren't into it were let off the hook, because I ALWAYS had moms who wanted to come in, especially for the parties. I'm a little neurotic, YES, but my parents were so happy because they felt that was fair, and that's actually how I ended up making the friends I have now! It IS a little time consuming getting it set up, but well worth it.
OK, so that's probably NOT the answer you wanted to hear.
Well, as one of the moms who's not in our "in crowd" and therefore out of the running most of the time, I suggest this:
This time around, try not to choose moms who have already done it--give someone else a chance. A lot of families in our town have two or more kids, and it seems those moms ALWAYS get a turn somehow, when there are plenty of other moms who NEVER had a chance.
If there are a bunch of newbies, choosing two is tempting, but then sometimes you get into power struggles (sad, but true). Put names in a hat.
If someone is a kook, or trouble, or undependable--I think it's safe to "lose" those names if they're going to be responsible for things like phone chain on snow days, or arranging the gift for the teacher.
But like I said, if a parent wants to be involved in a class, I think it's a crime to keep them out!