We have rented a house boat on Lake Cumberland and absolutely loved it. Lake was not crowded at all and we went in the middle of July. We brought my boat with us. We would move the houseboat every few days and use my boat to explore the lake and tube.
This is not where we rented from but it we return we will rent from this marina.
https://www.statedock.com/
Let me know if you decide on Cumberland. I can give you some pointer on where to tie off for the night.