Since I'm bored and have time on my hands, here's my ultra quick rundown of every Hyatt hotel in the Kanto area, in order of oldest to newest.

Hyatt Regency Tokyo
Pro: The cheapest hotel.
Con: Poor location for tourism. Pool and several restaurants have been permanently closed. Hotel is getting shabby, and is probably not long for this world.

Park Hyatt Tokyo
Pro: The best hotel with the best services and highest quality.
Con: Poor location for tourism.

Grand Hyatt Tokyo
Pro: The best Hyatt club lounge in Tokyo. Decent access to mass transit. Solid amenities. A really good all around choice.
Con: Avoid Roppongi at night time.

Hyatt Regency Hakone Resort And Spa
Pro: The most relaxing Hyatt.
Con: No pool. Inconvenient for tourism. Very little to eat within walking distance of the hotel. If you aren't wedded to Hyatt, there are many better places to stay at in Hakone.

Andaz Tokyo
Pro: The most hip Hyatt. The best pool. Very stylish, excellent food. Some rooms have amazing views.
Con: Location is so-so. New buildings have begun obstructing the view, especially the pool area.

Hyatt Regency Yokohama
Pro: Great base for exploring Yokohama.
Con: No pool. Sterile, cookie cutter hotel with bare bones amenities.

Hyatt Centric Ginza Tokyo
Pro: Awesome base for exploring Ginza. A very unique experience. Not for everyone, but the people that will like it will really like it.
Con: No pool. The people that will not like this hotel will really not like it.

Hyatt Regency Tokyo Bay
Pro: So new it's not even open yet. Designs look really nice. In a former life, it was arguably the best Hyatt Place in the world.
Con: No pool. The worst location for non-Disney sight-seeing. Not accepting bookings yet. Much about it remains unknown.

From what little I know about you, my top three recommendations would be Grand Hyatt Tokyo, Park Hyatt Tokyo, and Andaz Tokyo, in that order.

And of course, I would be remiss if I were not to remind you that I remain pessimistic that you will be able to visit in the fall at all.