When your children feel comfortable in a front float with a little kick, it is time to add the arms. Tell them that you are going to take one arm and reach for cookies in your pocket. Then, let the other arm reach for another cookie in the other pocket. Demonstrate how to swim with your face in the water. Let them practice until they can swim about half way across the shallow end. Explain that for them to be able to swim long distances, they will need to be able to breathe. Tell them that as their right arm (if they are right handed, left arm if they are left handed) goes around, their head follows their hand, exhaling as they swim. When the hand is where their pocket would be, their head should be turned toward their shoulder and they should be ready to inhale.
Remember, you will need to be patient and let them practice. Learning the American Crawl is like riding a bike or typing. Children usually need to practice a lot before breathing to the side looks and feels natural. However, just like riding a bike or typing, once the children get the rhythm, they will never forget it. After they are able to take even one breath to the side, they will be able to take others.
The entire process of teaching your children to swim usually takes about two weeks. At the end of that time, they will not be expert swimmers, but, usually, they will be good beginning swimmers who with practice will become strong swimmers.