What Should I Charge This Client?

I've got a client who I contacted with the intent of making them a website and then selling them SEO services. They already had a website, and weren't interested in SEO or Google Places. They asked for me to strictly give them an Adwords campaign for their business. What should I charge this client? I'm going to include a free $100 free coupon and offer to make a professional video for their website. They haven't given me a budget yet but are highly motivated to get it started and seem like they can spend some cash.

I've never done an Adwords campaign for someone else, he simply asked me to turn it on and off when needed. I'm thinking $100-200 a month? Has anyone done something similar for a client that didn't want to do the work?