Get a separate bedroom, as far away from your in-laws’ room as possible.
Agree to spend either the day or the evening with them, while reserving the other half of the day as private time for you and your spouse.
If your in-laws complain, tell them that with your careers and other obligations, you don’t have enough time to spend with one another.
When you are on your “alone” part of the day, go far away from the hotel.