Personally I would NOT want to be in your shoes any worse than you probably do over this. Although one of the things that will have to be remembered is the fact that there will be plenty of other people there to help him undo what ever you do as far as setting up safe guards. So that leaves you with only a very few choices:
1: Set it as McoreD above said, which will be safer for him and the computer.
2: Teach him how to fix these things hisself because he will be using it along with
probably others also that he gets to know.
3: Then teach him the values of security.
4: Also don't forget to make a backup before he leaves and let him keep a "copy" with
him for the times when he will need it.
5: Let Mom and Dad know that ALL the safety you apply to the computer will do no
good when he gets at school where others can undo it rather quickly.
6: Teach him to backup his work.
7: Setup passwords where it will be the most use (firewalls, ip filters, etc, etc)
I said all that above because there is almost nothing impossible and there will come a time when you can not be there to fix it for him. Then you can tell him it is NOT your idea so if he screws it up his backside will be yours.
Good Luck
Thanks
Dudelive