You Can't Play = A-OK
Don't force children to play together. Let them choose their own playmates. Author Heather Shumaker says:
Free play includes the right to choose whom to play with. Let children choose whether or not to include or reject a playmate. . . . This is what children need to learn: You don't have to like everyone. You don't have to play with everyone. You do have to be decent to everyone.