I guess I"m stuck at the 3 hour total time frame. We used to go after lunch when baby either went down for a nap in the car, or after the baby got up from the nap and then were leaving for home at 730.
Now, as for those folks who do not respect the baby's time schedule. My in Laws!! I can relate. Our child had difficulty sleeping through the night and sometimes would get up and cry at night. It was not to bad at home. Get up with baby, rock them for a long time and put them to bed. At some other place trying to do it quietly was a nightmare. One of the best things was the night we were at their tiny cottage and baby was up for a couple of hours in the night, keeping everyone up. Hubby and I told in laws that baby sometimes wakes up the house. They said it'd be fine. Then they saw what we went through. She stopped badgering us to stay the night.
then baby got older and she started in on "baby is having fun playing with the cousins, baby doesn't need an afternoon nap.' That's easy to say when you aren't putting the exhausted baby down at 7 pm!
Bottom line, all babies are different, some are easygoing, some are NOT. Some live by routine and some do not. No matter what, babies change and evolve. What worked for them yesterday, may not work for them today. Basically you tell MIL and FIL that as your little baby grows, it won't always be that way. You baby will be going for longer periods without a nap, will be able to interact more. (Hold toys and such). Tell them it won't always be this way, and it will get easier to schedule visits as your little on matures a bit.