Ash- Tell them your are having a holiday at the same time thats why you are staying in a motel and tell them you'll visit a couple of days and you would like to go out a couple of days. Like "family outings" that way they can still see the baby but you wont have to be at their house all the time. So say you are going for 7 days, Day 1: Your time, Day 2:visit at their house, Day 3: Go out somewhere with them, Day 4: Your time, Day 5: Visit them, Day 6: Go out somewhere, Day 7: drop past on the way home.
Even if when you are "going out" for the day just go to a picnic ground, or nice hotel/cafe/resturant for lunch/dinner.
Make out that you are having a holiday and you will see them as often as possible while still doing your own thing.

Thats my idea anyway