I'm looking for the best WPMU Facebook plugin to do

I'm looking for the best WPMU Facebook plugin to do as follows...

Ideally it would go something like this...

1) A visitor on either our website or FB page is presented with an offer via FB ad, email newsletter or other means to get $ dollars off on a product by liking us
2) When they do, they get a discount code that they can redeem via in person at the time of their treatment. (This is a medical procedure, and we will manually subtract the discount at the time of the transaction via simple Paypal transaction.

Additional question: Can we run two promos at once?

We are just about to create the Facebook page and our looking for any recommendations of what type of FB template/fan page to use. The business is botox and dermal filler treatments, mainly for women. A very vanity based business.

Please advise and thanks!

John Balla