I wouldn't worry about it at all. Go to the park with him wearing the shirt, and you'll park next to a car with a "My child is on the honor roll at xxx school" bumpersticker, and on the other side will be a "My son goes to Harvard" and after that, a "My daughter is a US Marine". Guy walking by with a dog will have on a sweatshirt that says "Property of M.I.T."