This is always a tough one. Generally, rallymasters have you bring more than you need, but then, better to have too much than too little.
In my experience, two packs of film is enough, but then you never know. Did Tom give any recommendations in his rally pack? I currently have three rally packs and can't keep them straight.
And I have had problems with these polaroid cameras before where they shit out 3 photos for every click of the button. Had to make an un-scheduled stop at a Wallyworld in Cedar City, UT, during last year's Twist-N-Shout rally cause of that. Talk about infuriating. Only thing I can figure, is make sure you pack the polaroid camera where it has some shock absorption protection.
Edit: I just read the Cal24 rally pack and there are no recommendations for how much film. I would say two packs would be fine, three extremely safe.