Phone Plans with Kids

We have a family plan now. We track our kids.

How does this work in the post divorce future? Who “owns” the phones? How does tracking work? If phones stayed with my spouse, would he have access to their location in Find My and I wouldn’t? We also have parental controls set up to limit screen time. What happens if he has control of all that but the kids are with me for the week?

I’m wondering about all this but hoping others have already navigated all this and can share what has and hasn’t worked for them.