Well, not cheap but that's almost a TMN to @deptfordmarmoset...Appreciate this is an old thread, but it's just bounced and I don't think anyone's suggested sticking a cheap folding bike on your rack and letting him ride it home?
How easy would it be to stick a Brommie onto a pannier?
Yep, I saw one dad giving his child a lift home through the park like that yesterday. I was a bit far back but I hope you can still see the child in a blue top standing on stunt pegs fitted to an MTB in this:If your bike can take them,maybe a set of rear bmx stunt pegs so he can stand on them. If you have QR's aint going to work. See kids doing it around here.
Be more Dutch :-)