Apple Watch for Kids setup can't sync to the kid's icloud Photos?

We have two Apple Watches for our kids, set up using my iPhone because the kids don't have their own iPhone. They each have their own Apple ID and they each have an iPad as well. I think I have just realized that you cannot sync their Photos (from iPad, for example, saved to their Apple ID in iCloud) to their watch. It only will sync with MY Photos app (to an album I designate for that purpose).

Question: Is there not a way to sync their photos to their watches, all using their synced icloud accounts? I don't want to have to manage a photo album for each of them. I'd rather their photos be synced between their devices without me managing in the middle.