We have 3 small kids and we live in Europe. We know how difficult it is to find a hotel that can take us all in one room.

I usually use booking.com to find an indication of the hotel's children policy. The hotel you'd like to stay at allow kids under 12 share a room with their parents, and all older child are charge EUR100 for an extra bed.

I ususally just book 2 adults, of course checked their children policy beforehand. If they don't allow rollaway we'd bring our inflatable matresses. If you are elite, you might be able to ask the GM for an upgrade in terms of getting your son into the same room without charge.