My son's birthday is coming up, and I'm finalizing the guest list. We're having his party at Gymboree, so I can have up to 12 kids and their parents. I have my core group of mom friends that I am inviting, but that is about 5 women and their kids. I also want to invite a few of my less close friends that I still see frequently.

My question is: the friends I see less frequently, some of them I am closer to than others. For example, I have friend A and B that I see maybe a couple times a month. But A and B are good friends with C and D that I see maybe once a month or less. If I invite A and B, C and D will know that they weren't invited, and I don't want to have any hurt feelings. Should I just go ahead and invite A, B, C and D? Is there some sort of rule you follow on who to invite to parties?