Ugh. Cascading parenting. Nasty business.
I know of only one way to un-parent in AE: split the layers. You can do it more than once, too. You can then go back and un-parent a section of layers at the proper point in the timeline, yet maintain the parent-child relationships on later split layer sections.
It makes for a lot of layers, and you have to be careful.
I'd set up label groups. Make all of the children the same color and then select by label group and set parent to none. Then when you've moved the parent, select the label group again and point to the new parent. Label groups are an AE essential tool that only a few artists use. I wish there were more colors because I use them in nearly every project.
Yeah, I finally figured that that was what I was going to do. Part of what kept me from doing that in the first place was that many of the layers already had label colors so assigning a "parented" color would override that, but in the end I knew it would be worth it.
I had a control null that was in the wrong place - just had to move it to the right spot and pick up where I left off.
Thank you to you both - Dave, I'llkeep y our suggestion in mind when I need to animate parenting over time. I'll have to try itand wrap my head around how to get it to work for me but I never considered it.