Upgrade. The Park rooms are the smallest in the hotel and you will have a much better experience in a Park Deluxe. Try to bargain for a Fuji view but am currently in Japan, have been for about a week, and haven't seen Fuji once -- don't expect too much at this time of year!
The Park Deluxe can be gotten with two double beds, so if two of you are willing to sleep in one of the double beds, you won't need a rollaway.