There are a few boys at my childrens primary still wearing shortd, if your ds is happu to wear them.its fine :)
My ds2 wont wear them at all anymore even.in summer and ds3 wasnt keen. Ds4 wore them.in sept/oct but hadnt done recently, if he wanted to i would let him.
Dp still wears shorts even in winter, i have had the odd comment from other parents in the playground that he must be mad. Umm no he just doesnt feel the cold much.
Some children are the same and dont feel the cold, i agree they look.cute! If he is happy to wear them and still has a coat, hat, gloves etc as appropriate its fine :)