The real answer is that Marriott will always recognize your elite status. The kicker is that the hotel has to know what that status is. With Priceline type reservations, the hotel will not know your MR# or anything about your elite status unless you tell them. If you call Marriott Reservations and have them apply your MR# to the reservation, you shouldn't have any issues with receiving recognition of your elite status.

As for getting both rooms upgraded, that really depends on the hotel. Per MR T&Cs, only your room should be upgraded (if an upgrade is available.) But if the hotel isn't very crowded, they may be willing to upgrade both rooms. Also, technically per the rules, only those in your room should get CL access. But again, most hotels seem to give CL access to everyone in both rooms. Just be aware though, that those in the 2nd room might not be given access. (Of course, a lot of hotels in the US don't really check what room someone is staying in and whether they really have CL access or not. So it is still possible that those in the 2nd room could still have access through one of the keys to your room.)