Would like to tie my game center account to an email so I can play the same account on my android tablet.
You can do this. Go to the settings (top right gear icon). In the settings there should be an email icon you can click to register. This will create the link.
I should also add, when you open the game on your Android device, choose the email login option. You can always change this by going to the settings and choosing to logout.
Adventure Agency Support