It is often not necessary to include an entire head in portraits especially with close-ups, however, it bothers me that the top of the mother's head had blocked out part of the father's face. Remember, too, that it is not always important to have the subject looking directly at the camera. With kids who are camera shy give them something to hold, or something to play with. Have them clown around a bit, maybe spin around in a circle, or jump rope or have them look at something to the side of you, or ask them how they would like there picture taken, and if they don't know, have an idea ready, like how about if you stand on a rock, or lie down with hands under the chin, or wearing a funny hat.....etc. I guess my point is to try to help them relax and have a little fun. Then keep the camera clicking! BTW. I like your photos.