Hi, Patty!
The rooms at the Contemporary are about 394 square feet. I know you were also considering the Polynesian, so just for comparison, their rooms are a bit larger at about 415 square feet.
A single room will get a bit tight with 5 guests plus a scooter. I know you want something on the monorail, but have you considered a Value Family Suite? At the very fun All-Star Music, you can get a Family Suite that has 2 rooms, a kitchenette, and 2 full bathrooms. One room has a queen bed, and the main living space has sofas that convert to pull out beds. These suites measure about 520 total square feet and will be much more comfortable space wise for your party.
The
Art of Animation also offers Family Suites. While a bit more pricey than the ones at All-Star Music, these suites are less than one year old and the resort is amazing! These Family Suites are 520 square feet.
The Family Suites are considered Value Resorts, so you will not have some of the luxury, but you will make up for that in space. I hope I have given you some information that will help you decide on your resort! Let me know if you would like to hear details on any other resort.