Mint was my first used, was straightforward and easy to get going. Still use mint.
I’ve always read it doesn’t really matter what distro you choose, just to pick one you like. That’s confusing to a noob because they don’t know why they should or shouldn’t like a specific one.
Mint is very simple to setup and works very much like a windows PC by default. Can even set it up to work like a Mac if you want to.
My son has had access to an iPhone 6s and iPad 2 since he was 1 or so (7 now). His devices have always been moderated to prevent him from seeing inappropriate content whether by accident or on purpose, and as he gets older I ease up on the restrictions. We have had little to no issue with him being attached to the devices, and my opinion is because he had mostly free reign over his usage barring bedtime. Even to this day he prefers to be outside playing.
I’m sure we’re all familiar with getting something we all wanted later in life than most people. We get super attached. I did get my son an Xbox one rather late (he had wanted one for at least a year before he got one), and he is attached to that. Because he spent a good amount of time dreaming and fantasizing about it.
My son is also high functioning autistic, (as am I), if that means anything. But this is my parenting style. Allow freedom within reasonable limits to promote individuality, unlike my parents. He sometimes watches the dumbest stuff on YouTube, but we all did and do. It’s not up to me to mold his sense of humor, I just make sure it’s appropriate for his age. Regardless if I think it’s dumb or not. I’m not 7 anymore.