I ran a bday party last year for mostly newbies. I built 3D terrain of 7 locations, but only had time for 4 or 5. The terrain sat on the fantastic locations maps, or was Hersocape. The party was called into a meeting with the Purple Dragon Knights as one of several groups to investigate odd magical occurances. As they were being teleported by one of the war wizards, something happened, and they ended up scattered in trees and on roads outside of a keep. Once they defeated the wolves and werewolves, they discovered that the keep had 7 portals to other places. This way, I could control how many locations I ran. When they went through gates that had several challenges:
Orcs in a ruined keep (using the ruined keep maps with styrofoam and Heroscape walls) about to sacrifice a unicorn. When they slept there after the battle, they were awakened by a bullette.
Yuan-ti in a dungeon (using mushroom cavern and drow outpost maps with styrofoam walls), the battle was too easy at one point, so I scattered lego weapons around the floor of the dungeon, and they had to roll to keep from being posessed and fighting their friends.
2 seperate mega block ships, each with crew claiming the other was evil. While they tried to figure out what to do, Sahuagin attacked (sharks too).
I also built a dragon graveyard (dragon graveyard map with megablock bones), a colesium where each would be put against a unique opponent.
The finally was a battle against the gargauntuan blue (a gift from my son's grandmother).
This works for newbies because you can control how much they do. If they have time, do more portals. If they don't have time, do less portals. They can get a sense of accomplishmet, and learn the game.