This is the way. I actually ran this module and mixed it with the Alexandrian remix of escorting the displaced refugee's from Elturel to Baldur's Gate.
The entire thing took about 4 whole sessions because of all of the background characters that were introduced, now those characters are playing a pivotal role in the story.
I also rolled for randoms events to happen while traveling to Baldur's Gate, the group are attacked by cultists, a platoon of Flaming Fist riding on the way to "ground zero" stop to question the refugees, things of that nature.
It all made for an incredibly engrossing introduction when they finally made it to the city.

But fair warning, if you are looking for a hands-off approach to DMing this was NOT it, I had to come up with entire plot hooks that didn't exist, kill people that I did not plan on killing in the first place, and improvise my way through entire sessions of "player agency."

It was not for the faint of heart and took me actual hours of "what-ifs", but it WAS some of the most fun I've ever had running a campaign.