Hetty, How often do they visit? Is your mum disabled?
Think would do what others suggest and make the most of having someone there to take over (go out somewhere). No need for you to wait on them!
Being practical isn’t being rude. You can smile sweetly, then leave them to it (unless you don’t trust them in the house to fix themselves a cuppa?)
Evolution - BBC2, Chris Packham
Talking throughout an exercise class

and say 'leave you to it while I get on with etc etc'.