An interesting idea for a mini horse, but rather puzzling, as it would have to be used from a kneeling position to avoid striking the saw on the ground.
If space is at a premium, would it be possible to mount the horse on a platform which you would stand on? It would therefore be braced by your weight, not the kids', so they could get back to their smartphones.

Attaching the two could be done by screwing short pieces of 2x1" to the platform top, then putting bolts through them and the horse legs. The idea may need a bit of refining, as I have only just thought of it and find computer drawing apps awkward.