The difficulty with naming a specific person, rather than a title, is that you want this agreement to be able to stand even if he moves to a different school or district, and as he ages to middle school and high school. (With respect to the latter question, I hope you are incorporating ways to be sure his own opinions are taken into account as he gets old enough to have them.)
Are you working with a lawyer on this? I would expect them to have opinions on this question, whose answer might vary locally.
