eeek
With the not helping with the tidying I would just be firm with them ie "ok time to wash up - do you want to wash or dry?" "do you want to vacuum in here or sweep the porch?" Kind of like a child offer them choices whilst making sure that the choices are what you want to do.
Most people wil ask at some stage if you want anything so when they do tell them clearly what you want - whether that be some cash or giving them a shopping list.

Our family tradition is taking turns - one person does one night and then the next night it's the next person's turn and so on so it all works out even. Maybe you could just say "ok we've got tonight and you can do tomorrow night".

What a niusance having to think about this - most people are so keen not to be a burden that you end up better off after they leave.