Yup, strictly 4 in the CSR regular rooms (unless you get a suite - I believe that those accommodate more).
If any of the 4 are young (~10 or younger), then POR has rooms in AB where you can book 5 in the room (with a fee for the extra adult). You could look to see if they have availability and switch. Otherwise, you are looking at two rooms for 5 people.
Have you stayed in a mod before? Personally, I would rather do two rooms at a value than have 4 + mom in one room..... but I need my space.