Do you have an old Windows laptop lying around that you refuse to touch because of how slow it runs Windows (Vista/7) today? If so, a new product called Neverware CloudReady may be able to help. CloudReady is FREE for Home use.
Neverware’s CloudReady will help you repurpose that laptop into a Chromebook that your young child can use. They have a list of models below that are certified to run CloudReady without any issues here: http://go.neverware.com/
The Verge has a great article below on how Neverware is helping resuscitate these old PCs for schools and other educational institutions.
http://www.theverge.com/2016/
Have you tried CloudReady already? If so, chime in with your comments and experience. I am planning on trying it out soon myself!