@Laura4890
Laura, trying to negotiate an additional cost with a guest can backfire on you. The option to send a guest a special offer will only be available for a guest enquiry.
So if you have received a reservation request your way to handle this would be to discuss with the guest in the message stream prior to accepting the reservation request the additional pet charge. But you have to either accept or decline the reservation request within 24 hours or you will be penalised for failure to respond. If the guest agrees to the additional charge, accept their booking request and when the booking is confirmed, via the message stream with that guest on the right side of the message stream you will see a tab that says 'Change or Cancel Reservation'. Click that field and then click 'Change', in the box that pops up, put in the price you have agreed to with the guest, and when the guest accepts the alteration, the booking will alter to reflect your pet fee and the guest will be charged accordingly.
The potential problem with doing this is Laura, the guest may refuse the alteration request which means that the onus falls back on you to either not pursue the extra charge, or cancel the reservation.....so, there is a risk involved.
The safest course of action for you is to ask the guest to withdraw their request because of the pet thing and submit an enquiry to you so you will then have the ability to send a special offer and not be penalised if the guest decides not to pursue it!
Cheers.........Rob