@Petrina-Noelle0 . Airbnb system works on a per person basis only. So options are to lock 2nd room and 2nd bathroom and only allow 2 guest bookings the master suite or they need to pay extra fee in advance. OR add another 2 listings, one for master suite only and another for single room only. This should allow 2-3 people to book both rooms (your existing listing) at the right price.
Just make sure its clear what is shared and what is exclusive use in each listing.