Actually, this exact topic (the permissibility of having five people in a room at the Sheraton Park) came up in this forum in July 2015, while I happened to be staying at the Sheraton Park. I ended up talking to the front desk a couple of times to clarify, and I concluded the following:
(1) the Starwood booking website will not allow a booking with 5 people in a room at the Sheraton Park.
(2) the front desk told me that maximum room capacity is 5 people, but that there are a maximum of two beds per room (either 2 queens, or 1 king with a cot; cots aren't allowed in the 2q rooms).
(3) in theory, if you phone the hotel, they might allow you to make a reservation with five people, but since you would be limited to two beds, and because of the ages of your children, I don't think a two bed room is realistic for you.
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I had a relatively small number of Marriott points (9k) which, after careful consideration, I ended up converting into 3k Starwood points. Our favorite non-
Disneyland hotel stays have definitely been in concierge rooms at the Convention Centre Marriott, but I was reluctantly forced to the conclusion that the Sheratons (both the Park and the one in Garden Grove), Homewood, and Staybridge hotels provide better value for the dollar.