As much as I love Google (not even a little, my love for that company is negative and becoming more negative per second) I would love to run far far away from it. Here's another ball and chain I need to break.
Where can I find a simple parental control access system for my phone and or computer that I allow my kids to use?
There are parental controls, but it's rare. FOSS projects usually aren't very keen on building systems of authority, even parental ones.
For smartphones check out /e/OS (Murena Smartphones). They added parental controls recently, not sure how good those are though.
For computers your best bet's probably a Linux with Gnome. They also added something recently.
You might be able to combine both with a custom DNS service, surely there's something out there for that usecase (NextDNS?). But that's already getting pretty complex.