Hey Chris. Dang! That's a slick setup! Yes, the toe piece will absolutely work, but I think the bigger issue will be finding the rental plate in that video. Even once you find it and get it mounted you'd still have to make sure he's in a boot that fits both an alpine binding (potentially even a kids alpine binding if that's what he's in) and also a tech binding. If you do find such a boot to meet all of those requirements then in my mind it makes more sense (financially, operationally, mentally for you and him) to just stick with a full blown tech binding.
It's a bummer there isn't more junior touring gear, but I've got a few ideas:
Hagan's Z02 Junior Binding
will work if he's in a junior boot.
Contour's Kids Touring Adapter
is a solid option, especially for the cost. We're expecting more of those in the coming weeks.
Otherwise if he has a tech boot that already fits him then a full blown tech binding is likely the best option.