I did this quest when it was new, and Dalaran was FULL of people, and there were several other people doing the quest at the same time. And I did it twice to help my sister get her pet.
Best advice: Keep running in circles. You'll eventually find them all.
I still have the book that ports me to the tower in Dalaran; even though I never use it. I used to use it to get away from the business of the city when Dal was active.