PvZ Garden Warfare -xbox 360 2 player profiles

I purchased and xbox 360 for my children. I created two profiles in the console, one for each of them. Only one is linked to a xbox live account using my e-mail address. My question is, in order for them to play with each other in this game, or any other,  do I have to create a xbox live account for each one or can I link my e-mail to both accounts?