What I've basically concluded is that the narrator decides if the player or enemies go first. Not the particular players and characters, just which side. Then, say the players act first, you declare what the enemies are going to do in what order (they'll still be acting last, but you declare first), then the players respond with their actions and what order. I let the players colaborate and discuss what actions are best, and determine turn order after. From there you just work your way down the turns starting from the first player down to the last enemy. If something inhibits your original plans, just let the player or enemy change them.
The players ambush the troll. The players get two whole rounds to act before the troll, so on their first turn Skip the bully, Ron the dreamer, and Elise the normal kid decide to threaten, search the room for hiding spots, and help the bully threaten (respectively). All goes according to plan, and now the real rounds begin. Since the troll acts last, the narrator explains that he is going to go for the Normal kid, since he gets targeted first, and try to pick him up. The players decide their order will be Ron > Elise > Skip. Ron explains that he can use his magic marker keepsake to create an escape route big enough for them but too small for the troll, so Elise and Skip decide use to Evade incase Ron fails. When the turn plays out, Ron expends an imagination to create a door in the wall and sneaks inside. Elise and Skip make a run for it inside of the tunnel as well. As for the troll, he tried to intercept Elise, but was failed, and the kids managed to escape in the wall....but what awaits them on the other side??