I decided to add several details to the truck: a rear view mirror, and ignition and a steering wheel.
First the rear view mirror.
The basic structure is a piece of cardboard with several little pieces hot glued on the back. For the reflective part I used a tea package opened up. Aluminum foil would work here as well. After spray painting the base I glued on the tea packet with some Elmer's.
In the below picture you can see the finished rear view mirror along with the ignition. The ignition is just a box spray painted black with a slit cut into for the key.
And, here is the key, just a piece of cardboard cut out and colored on with a Sharpie.
The steering wheel has been a bit more complex. First I'll show you my first approach, the one that Little Man destroyed! Then I'll show you how I "fixed" it. If your child is older or less rambunctious than mine the first method might work for you.
I cut out the wheel from a piece of cardboard. For the outer circle I traced a bowl and then marked the center by measuring across from several different points. The rest just required a little measuring. I can't recall where the pole piece came from, but it is a sturdy cardboard roll much like the aluminum foil rolls used in the basic structure of the truck. The hole in the center of the wheel was measured to fit the pole.
I cut the back side of the pole at an angle so that once glued onto the truck it would angle up.
The pole was spray painted, and then I traced the blunt cut end of it it to get two circles.
I then made a circle 1/4 inch outside the original circle. One of the circles needed to be a ring so I cut both the original circle and the second one. Below, you can see the sharpie lines are the ones I actually cut.
The solid circle I colored red with a crayon for the horn. The ring I colored black with a Sharpie.
The ring then got hot glued to the pole.
Once dry, I put the wheel on and then hot glued the horn to the end of the pole.
The wheel is sandwiched between the ring and the horn and is able to turn.
I knew this approach might not hold up to the toddler, and it didn't.
The second approach isn't as pretty, but it is preferred by the kid.
I tied yarn around the center of the wheel.
Then I tied all 4 strands together in the middle.
I fed all three through the pole. Originally this pole was just hot glued to the inside of the truck, but that didn't hold up well. Instead I cut a hole and stuck it through, then hot glued it. It has held up better this way.
The yarn then got fed through a hole in a piece of cardboard and I tied it in about a million knots on the other side.
Here's a view from the inside. In order to still turn the yarn had to be loose enough that the wheel can actually pop off the pole. Little Man doesn't seem to care when it is just dangling there, but it really bothered him with approach one when the whole wheel popped off.
The only thing left now is putting it all together...