I will not stay at my FIL's place for similar (but different) reasons, instead we either stay at a different relatives (which he doesn't mind) or stay at a hotel. If we stay at the hotel we tell him that we would be much more comfortable ith the kids and routines etc if we could go to a hotel, we also mention that that way it feels like a holiday for us and we can relax more. It is all true, if not the main reason for staying elsewhere. Maybe you could try something like that?