My FH and I are having our reception at a relatively small venue. It seats 150, and that is how many adult guests we are inviting. It was really hard to narrow the guest list down, but in the end the best solution was to make it 18+ which meant cutting younger cousins and friends' kids. We want to get the word out that we don't have extra space for surprise guests and also let the families know that we have some trustworthy babysitters lined up if they will need childcare during the reception.
For those of you who did adults-only, how did you tell your guests? What worked? What didn't go over well?