Grandma care did live with us for 3-4 weeks at a time and in the same house. There was also some judgement... with being my MIL and conflicts on personal beliefs and politics. There was also no break... she did not go home. (Well she eventually went home.) She was family so we did travel with her and had dinners and almost all meals together. An Au Pair would have to have 'off' hours and she doesn't necessarily have to travel with us.

Could an Au Pair be better? Or the same?

I do think we need our own space so I would need to find a place with a in-law suite or even better a cottage. (Luckily, I've seen a couple houses for sale with it.)