We stayed at the Equinox in Vermont in April. Made the reservation in February. The information MS had was that there was a 4/room limit, and we have 3 kids. I called the Equinox directly, and they confirmed 5 was fine. Then I called MS again, and they confirmed it with the Equinox.
We had an enormous, lovely room. As a previous poster mentioned, make sure you know what's included...breakfast was included, but they never told us at checkin. At checkout, DH overheard a guy say to his wife (they had just checked out) that if he had known that breakfast was included, they could have saved a lot of many (they had eaten elsewhere).