Line up 3 or 4 rows of 4 chairs, fill up all spots with kids and tell them that they are about to pretend to be on a rollercoaster and that they have to act out everything you tell them to do.
So you start off the rollercoaster with a bump and then it starts to go up and up and up an up, (exaggerating that is a huge coaster) then you level out a bit, cruising you can see the beach on your right, and the city on your left, (pause for dramatic effect), the roller coaster plunges incredibly fast straight down, it throws you left, then right, down again, up, down, left, right. It’s really speeding up now, oh no! The track is out ahead! You’re flying towards it at high speed! HOLD ON and you hit the jump, your all air born flying through the air, you’re really high up just cruising, there’s a flock of birds on your right, and you’re able to touch the clouds! Now you’re slowly starting to fall back to earth, picking up speed, getting faster, really flying now! One of the kids in the back row falls out! Falling really fast now, you can see the ground launching up towards you! And you hit the rails and your back on the coaster, well all except for one of you! Still traveling fast! Left turn, right, left, straight, and it’s slowing, slowing, and it comes to a halt…
Variations are only limited by your imagination, try placing in kids to do random entertaining stunts during the ride, make it crash, make them switch direction.