[ronyeh]

If your only goal is to have people play it and have fun, you should make it free but have In-App Purchases.

Many more people will end up downloading your game, and it may spread better that way (since it's multiplayer).

Now the question is how do you make money with IAP? Maybe keep some awesome game modes locked? Unlock them by getting enough coins (e.g., 100K). You can do this by playing enough, by sharing the app with friends on FB/Twitter, or by purchasing coins through IAP.

Good luck!