I don't know how well you know your son's partner, but it's horrible to tread on 'polite tiptoes' because there is a continuous 'guest' in your house. I would urge you to have a 'polite honesty' from the start and let everyone know that if anyone of you finds something annoying, irritating etc, they speak up!
I echo the bit about chores - again, don't let yourself/wife or son/lady be too polite.
Money - they have to pay something to keep up their own respect and remain adults sharing a house, rather than just 'moving into mum' and dad's house, if you see what I mean.
Anyway, enjoy and laugh a lot!