The reason that I mentioned the fact that Mike, Liz and April were caught between the Scylla of John and Elly's fear of them and the Charybdis of their fear of being embarrassed is that I think that we'd be at the point where Mike and Liz would start contemplating child-fleeing vacations of their own. Well, at least Michael and Deanna would maintain the tradition. Liz, I should think, would bring CHAOS on herself by being foolish and reckless enough to take her children with her instead of leaving them at home to think about the horrors that they selfishly, cruelly and criminally inflict on the parents to whom they owe everything and still freeload off of despite being capable of supporting themselves.
From Michael and Deanna, we would get the same speech from the caregiver that broadly hints that Meredith and Robin are sooooooooooooooo naughty and selfish and cruel and so defiantly insistent on the horrible, vicious lie that they are anything but an extension of their parents' will that poor Mike and poor Deanna have to have time to recover from dealing with two monsters who are not at all placid children who simply don't know what, if anything, they did wrong. We can also expect Mike and Deanna to feel a vague sense of remorse coming from that terrible, no-good, stinky voice that suggests the terrible idea that they're being idiots when it comes to the way that they think of their kids. The best part is that when Mike gets there, he'll finally realize that his parents were right to deny him time in the sun when he was too selfish and chaos-loving to appreciate it. Why, if they'd done that, it would have been entirely possible that he and Lizzie and April would have selfishly touched off a war out of sheer naughtiness.
Contrast this to Liz who would not see that her and no-longer-wonderful Anthony's foolhardy insistence on surrendering all their authority to mere children is why their vacations all suck. This would lead, of course, to a leaden and stupid Aesop about how they should have followed Michael's lead and not tempted fate, faith and chaos and not stupidly done what the insane Martian did and kept expecting children to behave.
That would show Kate for not letting the same mother who had no time for her monopolize the time of the grandchild she graciously gave her. It would also show the kids for wanting to go South where people would expect Lynn to forego shopping, snacking, lounging at poolside and guzzling beer and be something she hates more than anything else ever: the mother of small children.