We stayed four nights at Richmond with our family of six (kids aged 3 to 11). I was mostly happy they let us all stay in one room. It was a little tight but with a couple kids on sleeping bags on the floor, it worked out great. We folded the couch bed up during the day for more play room. We attended a conference at Kannai Hall, kiddy corner from the hotel so that was really nice. There is also a very nice park a straight walk East from the Hotel, beside the Yokohama Bay Stars Stadium. Breakfast was plenty for our family and there was a good mix of food for about any taste. And it's open until 10am so good for late sleepers like us:).
The only problem was we had to pay extra for parking. I choose the cheapest lot at 1,300 Yen a day since we didn't use the car once while we were there but had to use it to get there. That made the room a lot more so a bit of a bummer. Still, I would definitely return.