I've recently finished reading Dungeon World and will be running a session 0 as a first time GM for my friends, who are also almost completely new to the tabletop RPGs, and I'd like to ask you for some advice:
My idea for the campaign start (after we are done with character introductions, world creating and bonds descriptions), is that the PCs will be sitting in outdoors near a village having their lunch, with the food they were given by the village inn as a consolation for it being too full to take them in. Then, the first thing they see is a tinker coming their way and begging for some food. I imagine him as the sort of caravaneer nomad who gives travellers good or bad luck. Also, where they are standing, there is a big rock which seems like an ominous sign. The rock will make them hungry, sleepy, and then cause a fissure in the ground causing them to fall in a dungeon of undead creatures who are looking to sacrifice them and turn them into undead too.
How should I show the approaching the danger of that stone in the fiction? I was thinking about telling them that they suddenly feel very sleepy, giving them the opportunity of Defying Danger by either mental fortitude or shaking themselves awake. But I haven't thought of how to show the approaching danger of the fissure in the ground that causes them to fall. Also, I'm unsure of how to continue after they've fallen. I'm thinking of having some draugrs attack them and maybe a spike trap or two coming out the ground, since I will most likely also have a thief PC.