and theres bighead again, lol you got every part laying around imaginable!
Well it helps when I just picked up a truck load of Ody parts.

Also T-man got the axle I offered you. I will help out anybody when I can. Plus I have like 4 wheels now.
T-Man I think you should put hand controls. Best reason it is free. But think about it? With the Ody wheel it would be one size fits all. What about in a few years when you kids can ride it? With the Ody hand control they could ride at any age. Also the Ody wheel has a built in throttle control. If you notic in the pic the levers have a screw on the end. That screw is on a splined shaft. You can just rotate the lever on the splines so it bottom out on the wheel handle. It would take a few secounds to adjust the lever. You can do the same thing on the brake side but to adjust for smaller hands. Plus the polished ody wheel would look nice on your trike. Also has the light and kill switch right at your thumb. No reaching and grabing for kill switch. They really are nice wheels. You get a very good grip on the wheel as well. They fit nice in tight in your hands.
Pics 4 and 5 show the lever possitions. You could set it up for 10% throttle to 100% in about 20 secounds. I can also send you the splined shaft for the wheel. It is bent so I would have to cut about 10".
I think the Ody wheel is perfect for you and the kids. No peddal adjustments and one size fits all. Not to mention how easy it would be to install. No pedels just two cables and your done.
The last 3 pics show an Ody wheel I put on a handicap kart. Perhaps this will give you an idea how it would look. and how it fits smaller hands.
For my handicap nephew to ride this kart look where the pedals would have to be? With the ody wheel anyone at any size can ride this kart. Just slide the seat back.
After all that tell me it would look sick on your trike. And it's free.