Here's what struck me: what if one of those encounters resulted in a TPK? Would the campaign be over? SHOULD the campaign be over?
I want to turn this back around because I'm feeling like I don't understand the dilemma that you're facing:
What would happen if they instead followed the story path where it was leading them and then there was a TPK there? Would the campaign be over? Should it be over? Would you feel the same way about this issue?
I guess for my table - the published scenario for us is a framework that we're hanging our own gameplay on. If the players go off on a red herring path that I'm improvising and die it's no different than if they follow the tracks that the folks who wrote the adventure laid down and die. Either way they're dead and the story that we're playing will dictate whether or not they roll up new characters and we start the scenario again with the bad guys having advanced their plot in a meaningful way, roll up new characters and hit the reset button to start it again, or decide that the scenario was a waste of money because it couldn't keep our attention in the first place and it instead goes into the pile of "books to mine for stuff instead of use as written" and we move onto something else (that latter one has happened a few times - most recently not with a TPK but with Hoard of the Dragon Queen where I ended it early because the main story just wasn't keeping the players' attention - it was the wrong group to run it with. But the book still has useful maps that I've used in scenarios since then, so it's not a total waste.)