Family of 5 – with a 5 year old, 7 year old, and 10 year old (+2 adults) – can we get 1 hotel room?

How strict is Japan on # of people in a room? Do they really check? What if its a small kid?

Getting 2 rooms everywhere is expensive. In europe we wer eable to get away with 1 room and have the 5 year old sleep with us in the bed