Tango, after you have assessed your kids level in passing there are a few things you can do. If they are new, two parallel lines, about 8 yards across from each other, and just inside the foot back and forth. If they can do it well, challenge them with two touch. One touch to set the pass up, and the second to pass it back. If they can do that, one touch back and forth.
If they can long pass (done with the toe of the passing foot pointed down and in so the ball is struck on the laces of the boot) take groups of three, and have them execute two long passes and a short pass over and over. Besides the skill, the players have to think about moving around so the third and short pass is possible, A little conditioning thrown in here also. You can breatk the entire team up into groups of three and all work on it at once.
For a scrimmage, you have the two teams, and randomly put several pairs of cones wit each pair about one yard apart on your practice area. One ball, or two to get them thinking. To score a player from team A has to pass through a pair of cones to a teammate. They can pass to get to the cone or dribble. Again two balls will make them think tactically, and not let a lot of them stand around and watch.
If they can do these well, a great game is two teams of five players each in a two boxes about 20 to 25 yards apart. Box A kicks the ball to the players in Box B. Box B has to receive the ball and make 5 passes before Box A takes it away or kicks it away. to be successful the first girl will have to use some part of her body to take the initial kick and play it to a teammate. That teammate will have to be ready to one touch it to another. They probably won't be successful, if they are shorten the distance. If it is two easy for A, lengthen the distance between the boxes. Make the receiving box about 15 yards square. Again that can vary to change the game around a little.