Remember, this is also an exercise in
showing off the system. You're doing a sales pitch, ultimately. So I would say that you should try to make this exercise as polished as you can, in order to avoid bad impressions.
Also, think about
how you are going to present the rules. How are you going to do this in combat?
In general, you don't want to "teach the rules as you play". That usually leads to really slow, slow plodding. Lots of confusion, because different classes do different things. It's also like trying to teach the rules of chess (how pieces move, strategy, etc)
while you're playing the game of chess.
So, offer a 'tutorial'. Just drop a bunch of minions on the board, and go very slow. Tell them to just use their at wills for two rounds. Move the minions into convenient positioning, and encourage a person or two to use an encounter power that would be the most effective (minions crowded around a character, then instruct them to use a close burst).
Next, toss them into some actual encounters, and make the encounters
fun. I suggest taking a look at
this thread on encounter design to avoid "grinding". That way, you just don't toss the PCs into a 10x10 room with some kobolds and say "Go".
Give them incentives to use their action points and daily powers. Some players have a habit of hoarding their powers. Say "Go ahead and use it, this is the last fight". Or "I'll let you recharge it for the next fight".
Just remember that not everyone will share your views about what is an improvement or not. You may not even want to call them improvements, but rather changes to the system that you like. C
This is good advice. Additionally, just realize that some people
like some things you
don't. You might like the more streamlined system. Meanwhile, I have a player who loved how the 3e rules could build anything, right down to the most minute detail, and enjoyed spending skill points.
Also, realize you can't win 'em all; not everyone will convert. You might be lucky, you might have a full house of everyone that loves the game. But more than likely, one or two are going to be either reluctant or just not like it at all.