The boy can't remember the password ...?

If there is no possibility that your child does not remember the password and assuming that you will lose all the data you have on your system, you must perform a Windows restoration with the files that you can download from the downloads section of this forum.

Tutorial: [Hi10 Air] [Tutorial] How to reinstall Windows 10 for Chuwi Hi10 Air

Windows: http://www.mediafire.com/folder/nxlndr1f48nyf/Hi10_Air