I think if a child has coordination problems with the piano, you should remove the piano from the problem. Get him to play the piece on a table, and then all he will focus on is coordination. He will get used to the feeling of the hands and fingers doing small movements together. You must do this with the student though, and make it sound like a game. Usually they will just do it.
Then tell them to do it on the piano, but again make it just sound like a game, and then hopefully it should have solved the problem. Demonstrate to the child a lot as well, you will be amazed how much they will learn from watching and listening. If they are very talented they will probably play things back to you from ear. If so, you could play a one line melody to the child, and make him repeat it back to you. Do this a few times, then add one LH note, and tell him to repeat the passage, and I bet you will find he will play it, and then just get more and more complicated and see how far you can go with it.