Hi Toby. No dumb questions, just dumb people. (I think Scott Adams said that) You're not one 'cause you asked before trashing the bike. Hang around, enjoy the cynicism, smart remarks, and actually some really great people here that love to help out and of course give lots of opinions.
Search out a bike co-op if cost is a factor, otherwise you will have to seek reviews on bike shops and get opinions here. The bike is not toast, and a mech can either chase the threads or you replace the crank(s) with used ones from the co-op. It can be a pretty simple process. Be sure you son knows not to ride if the pedal comes loose again.
Get some pictures of the bike where you have questions and maybe we can help with some guidance.
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FB4K - Every October we wrench on donated bikes. Every December, a few thousand kids get bikes for Christmas. For many, it is their first bike, ever. Every bike, new and used, was donated, built, cleaned and repaired. Check us out on FaceBook: FB4K.
Disclaimer: 99% of what I know about cycling I learned on BF. That would make, ummm, 1% experience. And a lot of posts.