Group vacation money issue

So me and 5 of my friends are going on a vacation for my bday. We all agreed we wanted to get a big Airbnb to fit all of us so we got a 3 bedroom (2 people per room).

So I booked the place and divided it by 6 and sent it out to everyone what their portion is to pay.

So 4 of us are going for 5 days and the other two (a couple) are coming for 3 due to childcare issues. So they complained about splitting the payment 6 ways because that means they’re paying for 5 days while they’ll only be there for 3. But IMO they are paying for the room because we still had to get a bigger place to accommodate them.

What do y’all think in this situation?