They are always fighting for their right to be badly behaved. If someone offers you the privilege of accommodating you for a few days or weeks, it is basic courtesy and common sense to make yourself useful in that house unless your parents were too stupid to raise you properly.
Clean up
Offer to cook
Sponsor a meal
Buy fuel
Look after the kids
In any way that your presence makes their lives better, do it. This is not something that has to be taught to anybody. If you do nothing, let it be that it is because they stopped you from doing anything at all, not that you never attempted it. That should even make you feel uncomfortable.