The best way to calm your dog is to make the crate a pleasant place for him. Begin training well before you go on vacation. Place a couple of favorite toys and a treat in the crate to entice him. When he goes in to investigate don't close the door at first. Stroke him and talk kindly. Do this several times until you think he's ready to sit in there with the door closed. Stay close by so he can see you and hear you. If he barks, turn away from him and ignore him. As soon as he stops, give him a treat. He'll soon learn that when he's quiet good things happen. Gradually lengthen the time in the crate and your distance away from it.