Didn't dawn on me but I played one for years with great enjoyment, but a Mandolin would be a tiny enough instrument that a child could enjoy it with no problem. The neck is slim and thin and the double strings are forgiving.

It's a very cool instrument and can be gotten in the electrified mode if you want than and it comes in a lot of forms other than the uninteresting pear shape, without getting into the super expensive florintine style. I had a beautiful Aria solid spruce top natural M style with twin pointed horns like the one horn on the Florintine style, except on both sides without the beautiful top curly horn of the Florintine. I have also seen other very interesting versions of the Mandolin, one of the oldest known historical stringed instruments. EADG is the reverse of the GDAE usual tuning of the mandolin but many guitarists have tuned the Mandolin the EADG to mimic the intervals of a guitar. How exact and practical this is I don't know because I used standard Mandolin tuning myself.

The Mandolin is a lovely instrument and I shouldn't have sold mine, like so many others here that regret so many sales long gone by.

They are very durable as well. Mine had at least a seven piece neck and substantial bracing. Mine was not cheap, but I have seen a lot of inexpensive modern ones available.

Just another idea.