When I read the article I assumed it was a pedal vehicle, if it's battery powered that's different. Forget the fact it's a 2 year old kid, remember the fact that nothing other than pedestrians and wheelchars are allowed on pavements, for a REASON.
3mph, yep sure, then give it a petrol engine and NOS and Konis... etc. etc. etc. where do you draw the line?? Are the skallies that drive unregistered uninsured quads and motorbikes on the pavement OK too?