Though it shows on Marriott’s website as opening July 2021, it is not currently available for booking through Marriott, with no info as to when it will be. I don't see any U.S. OTAs offering it yet for booking, either. It is classified as a reward category 6, the same as the Swan and Dolphin, and it is being promoted as being a good choice for larger families and business groups; out of 349 guest rooms and suites, 149 are designed for occupancy of at least six.
Surprisingly enough, a travel site in the UK shows the Swan Reserve as bookable for arrivals starting in July 2021, but not any sooner. Searching for 2 adults and 3 children places you in a Family Suite. With the help of a currency converter, you should be able to get a rough idea about rates in $$$.
The UK site will not yet accept any 2022 bookings. Marriott normally accepts reservations up to 50 weeks in advance.
https://www.kenwoodtravel.co.uk/flo...a-vista/walt-disney-world-swan-reserve-hotel/