Linux is a commons resource. ABSOLUTELY, children should know how they can use the commons resource they have available to them - anything else, and you set up future generations for even more corporate control.
In case you're an un-educated American who doesn't know what the commons is, and why Linux is such an important resource when viewed from a commons perspective, educate yourself:
http://en.wikipedia.org/wiki/Commons
I know that commons is anathema to American industrial thinking, but alas .. this is precisely why its important to educate our children on what rights, responsibilities, and resources they have available to them. Linux is a very, very powerful tool which belongs to everyone. Microsoft Windows belongs to the shareholders of Microsoft - and nobody else.
Is using Android really your idea of learning Linux? iOS is a Unix variant too. Do you really think those facts are in any way relevant to the learning experience of children using them? That's pure technological partisanship, based on an agenda that has nothing whatever to do with education.