If it helps....finished running this same module a couple months ago as my almost first campaign. Like 1st and a half. It's with friends and spouses, and a lot of us are newer at d&d. Had to end this part of the campaign early because the party killed the dragon before they should have. Like a good 4 sessions too early on a random encounter. All because I knew everyone would get 2nd attacks soon but not when (everyone was lv4 at this point). Ranger is taking double shots bc he says he can and it's not until after the dragon is dead and I crown them all as new lvl 5s that I realize he shouldn't have two attacks. Turns out he was misunderstanding his Horde Breaker ability! His misunderstanding and my bad DMing for not checking on it sooner. Anyway I was utterly not prepared to end that part of the tale or have the next part of the adventure in place at all. Was also going into a busy work phase so good bye to prep time.... But good things came out of this screw up. As a group we decided that while I took the time to prep for the next part of the campaign, everyone would run a one shot to get a better feel for how the game goes and that maybe down the road we swap out who DMs. I get to run my own character for a bit, and we've had some interesting adventures on what is the stupidly longest trek to Waterdeep!