Not sure if this helps but I did find a way around the issue. We are a family of four, two adults, two children (5 and 1). After phoning a few properties i found out that it is perfectly fine to book a room with a maximum capacity of three as the baby in a crib does not count. This opened up much more availability when searching for redemption stays. The price and availability between three and four occupancy rooms is huge across the Marriott portfolio.