We stayed in THV in November -- 6 adults and one baby. Abby ended up in the pack n play in the living room, but that worked out fine. My daughter and son-in-law couldn't fit it in the second bedroom. We used the grill and also cooked some other meals. We all agreed that the THV were wonderful for us. We requested South end and canal view and were placed in 7030, very close to the path to Grandstand, not far from the boat dock, and just a short walk to the quiet pool and hot tub.
As for scooters, I know there are 4 HA THV with ramps, and it's possible to charge them at ground level. Don't know how they would work with the buses. We used the rental minivan, and also buses to get around WDW.