@Candice7, I note you offer use of an airbed for a third guest.
I strongly suggest you charge for a third guest, as hosting that person means more work for you (e.g. getting out the air mattress, laundering the bedding, extra towels, etc.).
You can add an amount in the Extra Person charge box.
I also recommend the following:
- request a Security Deposit;
- change your cancellation from flexible to moderate or - even better - strict;
- lay out a more comprehensive and clear set of House Rules.