Okay, for something like this where you're going to introduce the game to new people who are then, presumably, going to go off an play themselves, this is what I would do:
First, play the game. Play half of an adventure where they just worry about learning how to play. A nice introductory experience with some player choices and all three pillars. Do that for 2-3 hours. At least.
Teach them how to use their character. Teach them the dice. Teach them ability checks, and attack rolls, and saving throws.
Personally, I like beginning with a carnival/ fair with events. Archery and wrestling contests for attack rolls, pie eating for saving throws, races for ability checks, etc. Maybe an obstacle course.
Then have that move into an actual adventure. There's a problem. Have a small dungeon with actual combat and hit point loss. Something simple.
However, DON'T stop the game to continually explain things. Keep things moving and fun. Make it enjoyable first and foremost. Don't break the flow with constant corrections and the like.
About halfway through pause and explain what happened. Show your notes and explain how you made the story and adjudicated their actions and responded to their choices. Take a half hour to look behind the screen at the game. How you adjudicated and such. When you knew the rules, when you didn't.
Maybe some small suggestions and bits of advice. Like the importance of paying attention & thinking ahead for players, and managing the table & keeping things moving for the DM.
Then, after the break, maybe wrap up the game. Big climax. Maybe a nice cliffhanger. Make them want to come back.
And then explain how you would plan what happens next. How you prepped for the session and how you'd prep for the next.
Also, pregens are nice, but I'd say leave the background absent. Pick class, race, etc. But let them pick their background from a list.
Maybe include backgrounds on separate lists of paper (a half-page at MOST), with a couple skill choices and a couple personality traits. So they can just mark off the skills on their sheet. (The feature and details don't matter.)
That allows them to personalise their character slightly and you can show them where the skills are.
But That was quick! I guess the contagion has spread! 
