Sounds like fun! But I do think that Facebook giveaways are a bad idea. My experience is that the same people with insanely fast internet speed or use bots get all the prizes and nobody is left happy. When I was little I played Maplestory, and I remember they had giveaways through the game. They randomly picked someone online and that person got mailed such and such prize. Couldn't you do something like that?
Have you been to the SWTOR FB page? It's filled with mostly 4chan trolls who just ***** and moan. It'll be easy to win Cartel Coins there.