All MetalShaping - Jack of all trades, Master of none, and I tend to talk a lot

I have enough metal working experience to be dangerous. I am currently working on my Master's in Horticulture and I hope to retire from my student career. I am 44 and have probably been in school in some capacity for 60% of my life. I guess my hobby is tinkering/piddling. I enjoy gardening/farming because it requires piddling with a lot of different things, plants, equipment, irrigation.... I ran across the website looking for information on working with metal. About a year ago, my son got a hand me down power wheels, and we have been finding and fixing them when we find them on the side or the road. At some point, I got the idea that we could make a larger vehicle for him when he out grows the power wheels. Initially it was going to be based on a Mack Quarry Dump truck. He is five, so I have some time to accumulate tools, work on the design, etc. I am also interested in metal fabrication so that I can make special tractor implements and, well, whatever I need or want. An engineer friend turned me on to McMasters Carr, and then all sorts of lights went off in my head.