Can two people play the Hay Day game on one iPad? Can two people with different Apple IDs play the same game on one iPad? I am already playing a game, and my son would like to play, but he wants his own game, is that possible if he has his own Apple ID or Facebook?
Game Center only allows one sign in at a time, so you could sign out and then sign in another account. Most games also keep a local save file, so this might mix the results, but you would need to ask the developer of each app how it handles a log out of one Game Center account and into another.