I had this exact same problem last year when my daughter started JK. We hired a woman who does school runs only. She retired at the end of the year. This year my other daughter started JK so now I had 2 children to worry about getting to school. I asked any of the other mothers in my daughters class if they could pick up and drop off. We pay her $300 a month to do so, but I consider it insurance for the above reasons that Rachael pointed out.

Talk to the office, get some names of possible candidates (other mums, neighbours, etc.). Once you've found someone you are comfortable with, have them over for coffee a few times. Have your son get to know them so that might help ease his anxiety.

Good luck.