Looking for help - Multiple 500 points armies for beginners

I work at a youth center, and there I teach kids 10-12 years of age how to play Warhammer 40K. So far we have had two large armies, one Space Marine, and one Ork.

I am about to take it to another level, and my plan is to buy all basic codices and to build one 500-point army from each faction apart from Space Marines and Orks.

Adeptus Mechanicus
Chaos Space Marines
Eldar
Tyranid
Adepta Sororitas
Grey Knights
Imperial Guard
Chaos Daemon
Dark Eldar
Tau
Necron

And I would like some help to create 500 points armies from each faction, and I want them to be fairly blanced and fun to play... or something. And I want them to be 1 HQ and two Troops minimum (battle-forged).