Paul, what's your photographic experience? Have you worked with studio lighting before?
The reason I ask is because proper studio lighting is a skill that has to be learned, and having a first paying client isn't really the place to do that learning. It's possible that you might do your reputation more harm than good with this.
Where is your experience/strength in photography? Available light, outdoor shots? If so, why don't you do those headshots the way you are most comfortable?
If you are doing this for free and the client knows you're doing it to gain more experience, then fine. But if the client is paying (and paying enough for you to rent lights) then the client expects professional results. Are you confident of delivering that if you don't have studio experience?
Not trying to be a wet blanket here, but make sure you don't promise more than you can deliver.