no reason to be sorry - guess many of us can’t write perfect English
Your request seems quite comprehensible, just…I’d not recommend to use these constructions combined with a Strida.
A few thoughts about the part:
Obviously it is made of steel; that means you must bend the clamps (a lot!) to get them over the seat tube.
Once bent back and tightened will the harder steel most likely leave deep marks in the softer tube; perhaps damage it finally.
The angle of the clamps, related to the “kid connector”, doesn’t match to the angle of the Strida seat tube.
So, the clamp mechanism has to be modified anyway.
Generally:
The frame geometry and the wheel diameters of full size bike and Strida are much too different, their constructions can’t be compared.
I think it’s not assured that a mechanism like that will work without any (security?) issue on a Strida - just because it’s safe to use with full size bikes.
Simply imagine a triangle made of metal tubes; the corners shall be stiff like bone.
Three tube triangles - and in sum nine tubes, all their corners welded tightly together will create (in principle) a common Diamond bike frame.
Now consider that a Strida frame are just three tubes - and none of their joints is in fact fixed! All three connections are moveable in at least one direction!
One must not expect a strong frame - when the joints are loose.
Sorry - not feeling able to help in this matter - perhaps I’m getting old and thinking too much about safety…
I fully agree with Chris: a trail gator would put a lot of stress on the tiny Strida frame.
On top of that, I’m afraid the ride would not be very stable: the Strida has very little weight on the front wheel and the steering behavior is quite nervous.
I can already imagine what would happen if your kid starts to move sideways on his bike…
Follow Chris’ advice and go for a full size folding bike.