This situation starts raising YELLOW FLAGS, in my opinion. There's no clear agreement as to what you're expected to do, and on top of that the "clients" don't even know if they like your work. I would have expected your event planner friend to contact multiple photographers (you included) that would be willing and able to photograph the event and have her clients pick the one they like the best...that may be you...may not. The way it seems now, your friend if helping you out/hooking you up by "hiring" you for this gig but it bares to ask....what if the clients aren't happy with your photos?
You need to figure out exactly what's expected of you. This is a contract gig, and clear scenario for a CONTRACT.
....I can't get over it. I find it hard to believe that your firends clients would be willing to shell out $100 p/hour on a photographer without even ever seeing that photographers work. That's a lot of money to put down on a blind deal and could end up as a really bad deal if the cleints aren't happy with your photos. Both for you AND your event planner friend.
All bases are covered then.
