For better or worse I give my son (2) rides on my tractor. However he's on my lap, being held firmly and we're going very slow on level (paved) ground. Even that isn't strictly safe, but I feel that its safe enough to take the risk and he really enjoys it. I'd never have him with me doing 'work', you just can't hang on enough if you hit something with the bucket and you need 100% attention on the child or on the work so can't do both... I know as a kid I was allowed to do many things that weren't considered 'safe' today. I did my first tractor work at about 8 (solo) and was operating a 3 wheeler (and flipping it) even younger than that.
My son won't do those things, but I do think there's a middle ground between so safe you never do anything fun and taking reasonable risks. Really sorry to her about the article. Its a good reminder to us all to be safe, it only takes a second to have a serious accident on big equipment.