I gave this issue a lot of thought, and my husband still disagrees with me: he thinks we should charge per person over a certain number. But I don’t feel we should charge per person (and we don’t). We have a cap of 8, but charge the same no matter what. I just feel that charging more per person encourages people to fudge it and not really be honest about the number of people coming. I just raise the overall nightly rate a bit to compensate for fluctuations.
(But I make it clear that the city won’t allow more than 8 on the property.)
When we did have it set up to charge more, I noticed people always inquired or tried to book it putting only 1 guest in that field. I believe that when you charge per person people are too tempted to lie about it. Unless you are there to check them in and see for yourself—in that case, go for it.