Wintersg3, I've read pretty much all the comments on here (skipped a few of the harshly judgemental utter drivel ones) I would recommend instamapper for both live and past tracking. I've given my wife the account details because i've nothing to hide. Trust is a two way thing and i'm sure your kid knows that. Install it on your phone and give him the account details so he knows that your not round the corner checking on him?!... unless that could put you in danger from any of his dubious 'associates'
Otherwise install a security app like lookout where you can tack a phones current position (no past) as the 'locate' doesn't run in the foreground and it's a genuine reason for install incase the phone is stolen or lost...
All the best and keep your chin up