@Sarah977 Thank you for the tips. We already have something like this in the description but I find that the same folks that don't write the correct guest count are the same that don't read the description fully.
Even with the description about 10% of our guests show up with extra invitees. It's usually a mistake, because the website search defaults to 1 and then you might neglect to correct it; OR last minute friends come along and they forgot to tell me.
When talking with my future guests, sometimes I catch these mistakes from their reason for taking the trip, but I can't ask each guest outright if their count is accurate because it sounds like I'm doubting their honesty.
But I can punch up my description, per your advice. Thank you again.