I have a 2018 giant fathom sitting in the back of the garage with magura brakes, rs pike,, custom wheelset with dt hubs in a small if you would be interested. It would need new tires as the ones on there are seeping sealant, slx drive train and the fork might need to be service in the next 40-50 hours as it's been like 6-8 months since it has been done. There is a dent in the chainstay but it has been there for the last two years or more with over a thousand miles on it with no issues. Does not have a dropper as I do not like them on my hardtails for whatever reason but other than that it has been a solid bike.
I'm 5'6 and just a little heavier than your son so it should work for him, downside I am located in san antonio but I do ride purgatory creek and madrone weekly and could meet if need be.