Hi @Lucy478
I do get it/
I'm in sort of the same situation myself actually.
and I would LOVE if i could charge by room instead of by guest.
I have a 4 bedroom house that can have up to 6 beds and can sleep up to 8.
2 couples ( 4 adults ) would only use 2 rooms, which obviously costs me a lot less than 4 single adults who want 4 rooms
It's really tricky.
No solution really
I think what you have come up with is the only real answer.
The ONLY thing i might suggest is, make your price the more expensive option and state in your listing if staying midweek, the price is cheaper.
Guests are likely to be peeved to discover they have to pay more than they thought ( so may people don't read) but no one is ever unhappy to be told the price is going to reduce!
Just a thought.
Ps is you are replying to someone you need to tag them using the @ symbol - otherwise they'll have no idea you've responded. Airbnb continually suggest you go to the community for help, but don't bother to educate new users how the system works...