I've been on a journey to rediscover cassettes as a medium this year, both for myself and my kid.
For myself, the motivation was ownership over streaming and wanting to support the long tail of artists (or, anyways, the subset whose music I happen to like).
For my kid, my motivation looks just like yours: not wanting to give him access to smart devices and wanting to keep him away from screens.
The big learning was that, almost inevitably, one has to divorce the medium used for purchase from the medium used for consumption (which eliminates vinyl from consideration right there). When I started actually buying cassettes from artists on BandCamp, I quickly realized that I was paying way more for shipping costs and customs duties than for the actual media. Artists often offer the cassette including the digital album on BandCamp at similar prices to just the digital. Makes sense, if you consider that the digital doesn't add any real marginal cost. But, once you factor in the cost of tape stock, production, packaging/handling, often done by the artists themselves, I almost feel bad about taking advantage of their generosity. My intention is to financially support them, but I'm finding it hard to believe that, on the other end of all of these costs, there is any money left over for them. ...so, I tended to use the BandCamp feature for tipping/overpaying, but too much of that got eaten up by taxes and my collector / music enjoyment hobby just became too expensive over all, that way.
So, I stopped buying physical. My plan is to set up some kind of system to help me stay organized with self-hosted music files, and then re-booting my collecting hobby by buying one-time digital downloads on BandCamp Fridays or directly from artists. Maybe, I will also make mix tapes from time to time for myself or to give to other people. -- I think, in this context, the degrading-quality of analogue is a feature not a bug, because the ideal outcome would be for friends to enjoy single tracks from albums in degraded quality from the mix tapes, and then look up the artists they like and buy full albums as high-quality digital downloads, and support the artists that way.
For the kid, I got a vintage Fisher Price cassette player, and am finding it hard to believe that anything based on CDs could match the sturdy build quality. Also, with a toddler, it's a given that the media will be in contact with the floor a lot and scratch. So, this is another area where the cassette is a clear winner.
The third learning is about the actual process of making the cassettes: Right now, I have a tablet connected to a vintage tape deck through an analogue cable, and that's a surprisingly low-friction way to turn any kind of content that you can actually play into a cassette. Trying to stay within the digital realm to burn a CD means fighting the DRM platforms of each channel you're sourcing content through separately (with each presenting a moving target through time). That can get quite exhausting. I guess, if quality is not so much of a concern (which, with cassettes you're throwing out the window from the get-go), one can always use some kind of a screen-recording tool to record desktop audio, so, maybe, this is not a fair comparison.
Fourth, cassettes are easy to recycle: If I have a mixtape that I no longer listen to, or my kid outgrows a given piece of content, I can just record over it. I can buy boxes full of old cassettes as attic-finds on e-bay dirt-cheap, and get some use out of that stuff. This seems more environmentally friendly and sustainable than paying an industry to keep producing something that will inevitably be garbage one day. Maybe CD-RWs present a similar opportunity; not sure (never really looked into it much).
I also buy some new tape stock from Recording The Masters, though, because I dig what they're doing, and want to support them.
So, regarding that whole trend of bringing back physical media, my pick is the cassette.