I have run games for teens at my library in the past. I had to deal with the situation that each week different kids showed up for the game. Some were the same every time, others played once or twice and didn't return, or came four times out of the 12 weeks, etc...
So I ran a VERY episodic game. All the PCs were pregens. They were all 1st level the first week, and went up to 2nd level at week 3, etc...
The campaign idea was that the PCs were members of a huge wagon caravan, the survivors of a city that was evacuating ahead of a besieging army. The city had already been sacked once, and a bigger group of baddies was on the way, so they were fleeing, lock stock and barrel. The PCs were scouts, scavengers, and flank guards for the caravan.
Each week they had different "mission goals"; one week was food scavenging - they ended up going through a haunted house. Another week, they fought off a raiding band of goblins. Later on, they were hunting for a secret temple in the mountains where they hoped to find healing for many of the sick, exhausted city-folk in the caravan. Cliches are your friend!
My take-away was as follows: don't simplify the rules too much. But you control what they are exposed to, so if you want to keep them to essentials characters, do it. They won't miss the complexity of the other style, because they're still new enough it is ALL interesting.
Do keep things moving quickly. Always have a quick ambush or encounter of some sort (even just "Sarge" coming by to yell at them for dawdling) ready to go...
Minis are fun, as are battle-mats, but kids have great visual imaginations. Once they're used to seeing the action in their heads, they don't need props. But they do love them.
Don't be afraid to give some room for improv, silliness and general chitchat, but also don't be afraid to "call them to attention" now and then. They'll respect you and the game the more for it.
Lastly, have fun! Don't go with the idea of "teaching the game to a new generation" as if it is a recruitment mission. Go with the idea that having fun is healthy, and stimulating imaginations is always fun. The "game" is secondary.