I worked on an adaptation of the book as well. I was going to make it a cinematic, though. However, it began to get very long and very boring (about 20-30 minutes in), since I wasn't really cutting out much from the actual novel (eh... it is sort of uneventful in the beginning, IMO. The cool stuff begins to happens later on).
My tip is to add some filler. I definitely think cleavinghammer's tips are great. Perhaps let them explore Hearthglen before setting them off on the main missions. You can get a feel of Tirion's presence over the town. Although, as he said, you don't want to interject too much when the juicy stuff happens.
Another thing is that you should set it up so that the player gets a real hatred towards the orcs. Maybe have a village raided by some orcs, and you have to defend it (or something similar). The reason why I say this is because then the player will get a better understanding of the alliance's perspective towards the orcs--which is complete hatred, at the moment. The conflict between siding with Barthilas versus siding with Tirion will then become all the more epic.
I wish you luck on your map, though! I always love to see the adaptations (mostly OutsiderXE's campaigns). It has that realistic feel to it since the lore is considered candid by most people, more or less.
EDIT: Here is a pic of Western Plaguelands that may help:
For one before cata:
http://www.imageslime.com/img/Western-Plaguelands-map-3519.jpg
Perhaps you could incorporate some of the neighboring areas if you are looking for ideas on what to add to the campaign.