Provide enough fresh towels, I would say four each should be plenty, or give two each to begin and provide another two each mid way. Personally, this is a home stay not a hotel, so sheet changes should be more along the lines of what you would do a home. Most people change sheets weekly, so I wouldn’t feel the need to change the bed during a six day stay. I find most people prefer room privacy rather than having the host go into the room while they are there, so I think you’ll find this works works in your favor with guests requiring less in the way of room services. You can always ask, but I would almost guarantee the answer will be that ‘the room/bed is fine thanks, towels would be great’ (if you had only started with a couple each). Personally I provide everything I think they will need so that I don’t need to bother them too much.
Whoops wrote this way earlier but before I could hit send, the whole thread had filled up!