It is actually not very special dietary item. It is just the way they slaughter animals in Islam. It could be chicken, beef or lamb. No pork allow at all! And there is no halal pork. And you can find them easily in superstore, Walmart and Asian stores( Indian, Pakistani and Bangladeshi etc.)

It is actually tastier and you can store them for long time because of the way they slaughter animals.

You can either buy Halal food for all your family so you don't need to shop for 2 different meat or you can ask them to bring his/her foods.

Hope it helps