@Tami1. Hi Tami, if you do accept consider the fee compared with boarding fees for 2 cats for 2 months as well as the potential clean up fee. You probably also need to send them a pet questionnaire and agreement for this length of stay.
With cats they will scratch as well as spray and even if short haired drop hair so your carpets and rugs are fair game. Do you have a scratching post, areas they can sit in the sun inside as well as outside? Kitty litter trays; where are they going to sleep?, etc. Its possible they are bringing all these things and are responsible pet owners but you need to ask and get it in messages so its in writing. Invest in some good de odour treatments as well.
I host pet friendly but they are really only suitable for dogs as cats would need to be kept locked up at night, given all the vulnerable local wildlife.
Just my 2 cents but I think your gut is telling you something. Why not offer some price special promotions- spread over multiple bookings it may be cheaper and less stressful in the long run.