Yes, it took me some time to adapt to the fact that there is much less time for your own projects. Now I'm totally fine with that. The good thing is, the kids grow older and suddenly time windows become available again.
I once read that about 80% of the whole time you spent together with your children is spent before they are 10 years old. So your are right when you say your want to spent the time with your children now.
I can relate a lot. Having the momentum on your side is the main force that pushes such a project forward. Especially if you have family duties that ususally consume most of your free time.
As long as children are smaller even things like scheduling time for your projects don't work very well. Usually because unexpected things happen that need to be handled. Sickness, children waking up early or taking longer to go to sleep, etc..
I like the mental model and I have often witnessed the meddling you mentioned.
My favorite kind of meddling:
The current state of a software product is presented to C-Level. After listening (usually) for a few minutes one of the most senior people in the room starts expressing a strong opinion about how a certain color should be changed.
Now the color scheme discussion starts. The complexity of enabling an interaction of a user with the software through the interface is not discussed at all.
At least changing a color usually doesn't harm the usability too much.
I once read that about 80% of the whole time you spent together with your children is spent before they are 10 years old. So your are right when you say your want to spent the time with your children now.