Man Al! That's great thinking and parenting by the way. You did Dad right and it shows in your family. Steven's been sending it! To the machine shop...
Practice tree is great but those buttons are nothing like what you have in a car and can throw you for a loop. I guess you could get a full size tree and actually suit up and practice in the car if you had the correct tree distance.
A few JR's I've seen actually have to have a little disc around the outside of the wheel. The spoke rims are so close to the ground that the beam breaks when it's rolling in, turning on the top light, then it goes out because the little thing goes under the beam. Really confuses the kids sometimes. So, yeah, staging is ultra important no matter the size of the front tire.