Cool video! I've been trying to train my 5 year old to ride a bike. Converting to a strider type setup seems like the ticket. Hadn't even heard of this before thanks.
The strider is rad! It teaches the kid to balance and turn without having to deal with pedaling. Once they have the balance down, put them on a pedal bike with no training wheels, give em a big push and off they go.
I second neileither's Strider love. My boy isn't on a real bike yet, but his balance has come a long way already with this one. He was SUPER slow before because he wouldn't even sit down, just walk with it. He trusts his balance sitting down now and is getting a lot faster.
You should ride your bike like he does when you are with him. Pushing with your legs and then goof off picking your legs up and coasting... if he sees you goofing off doing that he will start to try it too. I think those bike are great!
That's never been an issue for him and didn't come up in any of the research I did on it ahead of time (MTBR forums etc) so I can't imagine it's an issue. From watching him a lot the only way his foot would end up hitting that back wheel is if he was pretty far off balance to one side and in that case he'd be crashing anyway...which he has done a few times, just not on video :)