I charge extra for pets or when I have to set up the airmattress, but the only way it works is if guests read the listing and increase their number of guests so that there are more than 3 (the base rate covers 2 sharing the bed). Often I get a guest with a dog and have to ask them to change their booking to 3 for the dog, because I spend way extra time cleaning after a pet, including renting a carpet shampooer.
Likewise, I have 2 guests arriving tomorrow who have said they are friends and have not asked for an extra bed. Do I set up the extra bed? They haven't included 3 guests on the booking, so technically I haven't been asked for the extra bed and bedding.
They will arrive tomorrow, expect me to rush around to set up the extra bed. I'll be forced to ask them for more money (awkward) and they will give me a bad review because I wasn't "ready" for them and it wasn't as good a deal as they thought.
I'd love to be able to add a fee for pets or an extra bed just they way you do for "guests over ______".