but it is the responsibility of the parents to minimize the inconvenience to all of the other people. If that means driving instead of flying when the distance is reasonable then they should drive. If that means the grandparents are the ones that make the trip more often then not then that is what they should do. It's really just common courtesy not unlike not taking your infant or small child to the movies. The child cannot be expected to behave itself because it is a small child so the parent needs to make the decision to not take them there in the first place.

I'm sure there are circumstances that require flight with an infant or small child but not many for the most part people are just choosing to do it and so they are responsible to minimize the affect on everyone else.