How to decline politely re: homestay

My husband, 6-year-old son and I will be visiting Japan for three weeks - Niigata and Kyoto for most of the time, and somewhere near Fuji-san for a day or two. We have friends (good friends, but not extremely close/informal) in Niigata who will be hosting/showing us around.
We understand that our friends have a very small home, but we anticipate that they will ask us to stay with them while we're in Niigata - they're extremely gracious and polite people. We would be happy to stay with them for a night or two, but our son is very energetic and it would be much easier and more relaxing for us to stay at a hotel most of the time.
How do I express our wish without causing offense?

Second question: the husband of the couple we're visiting has offered to go with us to Kyoto to show us around, as it is one of his favorite places. How do we handle room arrangements? We would be happy to pay for his room, but again, do not want to inadvertently cause offense.

For your Niigata friend, the explanation you just wrote sounds just fine to me.

For your Kyoto visit, is your friend really planning to stay for the night? A lot of people just make day trips. But even if he is staying over, you don't have to worry about paying for his room unless you're inviting him to your wedding. Maybe you can just buy him dinner, but if he says no thanks then be it.