Another thing to remember, do you really need whole people. Have a look at party photos, The more you go back into the room the less you are going to see of the body, so you can make parts invisible from the chest down. Also not all of the people will be looking towards the camera, so all you will need for those is hair and an item of clothing and no body, in one of my images i have a girl on a hill looking away, its just hair and a dress, no body. but really the best way to do it is has been said layers. Gives you a bit more control