This does seem like the best way to do it, in the spirit of the game, especially for our very first ever game of DW. I do worry that my players will be either a) struck with option paralysis or b) lose investment in the world if they feel like it's JUST been made up... by them. We'll see.
The trick is to not just tell them "And now, make a map!" but to ask a bunch of pointed specific questions. Like where the fighter learnt to fight (it's probably on the map!), who the thief ripped off recently (the NPC lives somewhere) and so on. For my group, we just played on fantasy tropes.
The players started in a jail cell and broke out, managed to flee the city (mid-siege, no less) and then got to work drawing a map. One of them made a forest with a grove and a pond in the middle, called it "The Grove of Sudden Death", and I went, well, it's a creepy forest, there's probably a ruined creepy tower in there somewhere, right?
When they went to see it, the bard decided to see if he could read the markings over the tower's gate. He succeeded his roll and I got him to tell me what was written. And the dungeon was immediately declared an ancient elven mausoleum. We had elf mummies and everything, it was awesome!