When you are thinking of getting any of your children to learn to play the guitar think about their age: Children under 8/9 years old tend to struggle with motor skills when it comes to playing the guitar. Holding the guitar is often a problem as well, even when the guitar is a small one.
In cases like this the Baritone Ukulele may be the answer, since the Baritone Uke does have the same first four strings as the guitar. The advantage of this is: The chordshapes for both guitar and Uke are the same.
Anything which your child has learned on the Baritone Uke may be transferred to the guitar once your child is a little older.
Since not every child is the same it still makes sense to start out with guitar and see how your child gets on with the instrument. If holding of the guitar is too much of an issue try a Baritone Ukulele.
Cheap Baritone Ukuleles can be bought for a similar price as a cheap small guitar. The Baritone Ukulele can also be used as a small travel instrument.
Good luck and hope to see you soon again,