The room was not big for our family of four (two afults, one 7 yo and one 3 yo) but we had 3 beds and some space for our backpacks. Breakfast included was good and had provided Continental alternatives.
We used the hotel to go everywhere in Tokyo and with a Metro card this was a perfect spot, Being a little off when you wanted to recharge.
As a children’s family we thought the nearby Shinjuku park would be perfect, but that is more for sightseeing and temple visit.
But the Toy museum and the nearby facilities (read soccer court and playground) was awesome for both children and we also visited and liked the next door Fire Museum a lot.
If you want to stay nearby a leissure park, try something closer to Yoyogi park instead (we spent almost one day there when visiting Shibuya crossing etc.
To sum up. No extra luxury, but good base to see Tokyo!