Grouping keyframes of different objects for animation

Hi,
I’m looking to somehow group keyframes so they will appear as ?one object? on time line.

First my situation - I have fave few objects with single parent. I’ve made animation, where parent moves across scene, and it’s children also moves on thier own (relative to parent). Also some of the children have animation applied to shader (mix shaders and mapping node). I will have other objects in scene also.

Second what I would like to archive - I’ve would like to somehow group all these keyframes, so later on, I could easily tweak timings.

Third what I’ve tried - I’ve read a bit and it look like NLA would be ideal solution. Most of tutorials are about character animation. But I can only (I think that only- NLA is new to me) create action for one object, not many of them. I’ve seen one solution that I could create custom rig for parent with objects and animate the rig instead of separate objects, then create action for rig. But it doesn’t solve problem with shaders animation.

Fourth mixed solution - Is it possible to somehow mix NLA with keyframed animation?

Are any of these things possible?