Non compete clauses for a sub-contractor

You can add whatever you want, but that doesn't mean (a) the at the subs will agree to it; or (b) that the courts will enforce it.  If you tailor the clause narrowly  to protect your legitimate interests, there is a good chance that it will be enforced, but the broader  you make the clause, the less likely it is to be enforced by the courts.  A local attorney would have a better idea of how far the courts are willing to go.