A Grand Project

Each year the kids' AWANA club hosts a Grand Prix (pine wood derby car) race. So guess what I'm building! Here are a few pic of my progress so far. Each kid pics out a toy that we try to copy.
I'll rough cut with a back saw or coping saw and then fine tune with a chisel. The sanding will be done by them as well as most of the finish. Of course they can't pick anything easy. Somehow I have to figure out a low rider and yet not create any friction on the wheels and still meet the size requirements.
One "fun" design we're trying this year are working lights on the low rider. I had to hand mortise out a slot for the battery pack. It fits pretty snug, so maybe I am ready to try a true mortise and tenon joint.