We're planning a family trip to NYC in the fall - arriving Wednesday and departing Monday. My parents are not big travelers and only have enough points to cover 2 of the 5 nights. The weekend rate is significantly less, but only appears available online if you arrive Friday.

We are trying to figure out how likely it will be that Marriott would allow my parents to use points for the first two nights and then get the much lower rate starting on Friday, but not make them check out and check back in Friday? Obviously they want to pay as little as possible but do not want the hassle of moving rooms.