For what it's worth I had the permanent retainer on the bottom installed when I was like 17 and it came out on it's own probably 8-10 years later. It became the bane of my existence while it was there. Constant cuts/irritation on the tip of my tongue from trying to pry out food that got stuck behind it, and flossing/brushing around it well enough to satisfy the dentist was a chore. Anything and everything you bite with your front teeth will lodge behind it and be extremely uncomfortable.
The next time I went to the dentist they wanted to recommend an ortho to install a new one. I told them not a chance. For less than $500 out of pocket, my general dentist got me three pairs (top and bottom) of invisalign-style clear thingies. They told me they're supposed to recommend I wear them all the time to keep my teeth in place, but realistically wear them to bed every once in a while and as long as they're comfortable and not causing soreness it's a fair indication that my teeth aren't moving.
I understand it's a hard ask to expect a kid to be responsible with wearing anything they can choose not to, but if they don't the burden will be on them to get their teeth fixed again when they're an adult. Based on my experience as the wearer, I'd take the clear retainers over a permanent 11 times out of 10.