Park Suite
I would never fit more than 4 (2 adults plus 2 children) into a Park Suite, unless one wants to sleep on the floor.
I had a Park Suite with two twins (larger twin, but still smaller than double) and it fit two just spaciously. The living room is just for that, entertaining, so the couch does not pull out.
One word of caveat: the Park Suite's maximum occupancy is TWO (according to the hotel). Do make sure you have Gold Passport or Reservations here document it here, or you will be charged a 5000 Yen per person fee for any additional persons with or without a roll away.
If you have Reservations document that in your reservation, the Hotel is glad to provide you with a roll away, at no additional charge to accommodate the third person.
Honestly, 5 people is really pushing it. The bathroom is large, but can accommodate 2 spaciously and comfortably (call me spoiled, but I am used to 600 sq ft bathrooms/dressing quarters).....the Park Suite has a really nice dressing/make up/bathroom area, that's just set up like a master bathroom in a respectable home...... again, over 3 occupying the suite would be pushing it. I suggest getting another room and they would be happy to arrange them close together.
All in all, the service at the hotel has never failed me.........well except once at the Girondole, the lobster served was mushy.....I had to reject it twice before they suggested bringing a monkfish......