I'm sure this has been posted on endlessly but the search function is useless, so here goes...
Despite us addressing invites clearly to adults only, we have received an RSVP for the entire family. They are my parents friends who I know reasonably well - and my parents assured me I could just write them an email to let them know about the adults-only policy (FI and I are hosting the wedding, so having my parents tell them doesn't seem approriate).
So here is the question: In this email, should I provide any explanation for WHY kids are not included, or just simply state that "we have had to make the decision to have an adults only reception." (followed by offering to help them find babysitting etc). Our reasons why are that it is a small venue (no separate room for kids and also we are near capacity as is) and it is an evening reception with dinner, dancing and open bar - in other words, an adult party!