Hi, looking at finding the impossible! I’m after a turbo trainer set up for a kids 16 inch bike, to use with zwift! Can anyone help? Thanks in advance 
I just put my son’s mtb on the Zwift Hub trainer using a Zwift cog and riser block. You just have to ensure the chainstays are wide enough. Turns out my son’s tiny mtb has wider chainstays than my road bike, and one flip of the hub spacer adapter later was all working well.
The Zwift cog goes down to 8 speed chains. Anything below that, you may be able to bodge it anyway.
I’m not a biker myself, my sons just getting into it and I’m not going to lie I’m clueless 
He’s got a boardman 16 hybrid, no gears just bog standard bike as he’s so little! It’s a minefield especially on a budget 
That’s a nice bike!
Don’t think it’s going to be easy/cheap to get it onto a trainer for Zwift though.
- the single speed/lack of gears will make it hard to work with a direct drive trainer (one where you remove the rear wheel and the trainer provides the rear wheel equivalent
- the alternative to a direct drive trainer would be a friction trainer where the rear wheel presses against a roller, but then your rear wheel is too small for these devices
I have seen a few people asking this kind of question, have yet to see a simple solution though, sorry.
Here’s another article I found when I was looking into it myself, maybe it’s useful for you: How I Set Up My Kids’ Bikes On Zwift | Zwift Insider
(Note: Zwift have discontinued the kids account option, so they need to use a standard account)
Just wait for him to grow and layer up in wet weather gear and head outdoors it is for now then I don’t mind spending the money if I know it’ll work for his bike, just no idea what to get 
Ok so a kinetic trainer could work?
Looks like it has a nutted rear axle. IDK any trainer that could work with that. The ones I know can do QR dropouts and thru axles. They may exist, but I don’t know of any.
Feedback sports Omnium overdrive are advertised as working with 16” wheels, add a wheel speed sensor and you should be able to use virtual power on Zwift.
There’s an older Elite turbo trainer that works with my son’s 16” hybrid bike. Elite Qubo. I had success using that and a cadence sensor to get my son on Zwift.