Hello @Francis88,
You can set a base price equal to the two person rate. Then, under additional costs, you can add a per person rate.
Example (making up numbers here). Base, $50 for first two. Then $15 for each additional, so 3 people would be $65, 4 would be $80. You can do all this adjusting under pricing.
However I do not necessarily recommend this - you might do better with two separate listings for each room. That way you would avoid the possibility for two people to book, and then each take a separate room. As it is listed, whatever size the party is, they book both rooms. You could even have a third listing with both rooms listed (for a party of 3-4). If you do choose this option, you will need to pay attention and block the individual rooms when the double room books, and vice versa. This can be complicated.
I have two rooms available, but I don't have that third listing. However, I do have a link to each booking on the other's site. That way, at least people will know about the extra room.
