That's a great plan. I know how to do that. It might take a few tries to get the volume to match. But heck yeah! Great idea. Thx!
If you can use a repeat section form the LP that would be best.
More likely than not the CD and LP will not match well. The reason is that significantly different dynamic range compression are usually used in the two mastering techniques.
I would do this fairly soon, as more likely than not more impurities will come to the surface over time. That is my experience.
CDs are also a problem as they deteriorate over time. I am finding increasing numbers of my older CD, are becoming unreadable on any of my players.
I am now finding that those that have claimed that this would be a problem have been correct all along. I was a sceptic. So far it is just a few, but I am running into this more and more often. I have lost a few treasures already.
So CD and I guess laser read discs are not a satisfactory archiving medium. Magnetic tape is not good and I doubt solid state hard drives are either. So probably the LP disc is the best we have got.