Personally, when I get new players of any age (new as in never played before) I run the first session or two with an aim at teaching the rules. So for example an encounter that results in combat ... have AOOs in there, spells, missiles, etc to teach line of sight, damage, to hit, and so forth. Maybe throw in a grapple. Then add a roleplay only scene and so forth.
Talk to your other players and inform them that you want the newbies to grab a bit of spotlight, and ask them to stand back a little. Let the newer players make their own decisions, or if the others wish to inform then to do so in an instructive manner. For example:
New Player: I charge the orc leader past his bodyguards
Old Player (bad example): Don't do that you'll draw AOOs and they'll get to hit you and then you'll probably drop and it will be a waste so move around them.
[too much information with little instruction]
Old Player (good example): Do you know about AOOs? An AOO is a ... and if you move past the bodyguards like that they can ... etc etc. However you might have a plan that I've not thought of.
[information, instructive, and puts the result in the player's hands]
As for the ages, I'm assuming they're related in someway (children of friends, sons/daughters) to the current players? Because the first house rule would be to ensure their parents or guardians allow them to play. I know it sounds stupid, however as a teacher I know the problems that might come up.
D