Reasonable weekly contribution when staying with retired parents

[C44D]

Myself and DS age 11 are going to be living with my parents (both retired) for approx 6 weeks, sharing a room together. They are not expecting us to pay ‘rent’ but I want to contribute to food costs and obviously their bills will increase with extra washing, hot water
What would you say is a reasonable weekly amount to contribute?

When I visit my mother for holidays I cover
all the food costs, take out for lunch, etc. to make up for the utilities used.

Yes I would say buying as much of the food as possible and generally helping out with house/ food prep/ garden work etc. Taking on as much household chores will help far more than contributing to water bill as your % won’t increase that much

Most people wouldn’t want or accept actual cash. But you could take them out for dinner or buy garden plants etc as thank you?