Help with ad pricing

I am starting a niche social network/business directory for a niche that has expressed a lot of interest. We have around 1000 likes on facebook 5k twitter followers and 300 web signups for just our landing page. We were also lucky enough to work closely with a friend of ours who owns a pr company that is going to connect with their several thousand press contacts about our company.

What this means to me is that we'll be experiencing a ton of traffic for our launch and with our systems in place we are going to be having a lot of long tail traffic for years. I have adpeeps in place with ads ranging from 200-1100 depending on the ad location. This is all set up in an automated form.

This brings me to my questions. I was wondering what you folks think I should charge for my pricing structure. Should I try sticking with my current pay per ad model or should I try CPM ?

 

We are thinking about mixing cpm ads with monthly flat rate ads. This is kind of a last minute decision I guess as our site is launching tomorrow.

 

Being that small, I would look for other revenue streams besides advertising sales.