1. Family portraits are large about capturing relationships and interaction and that's pretty tough to capture when everyone is far away from each other, so the first thing I do is get everyone to squish together.
2. I like to get everyone's heads fairly close together which can be done by having everyone sit down. Even if the kids are dramatically different heights, sitting down brings everyone closer. It can be as simple as just sitting on the ground. Look for nice colors, textures, and clean backgrounds. Steps and benches work great too. There are tons of options!
3. One of the easiest way to dramatically improve your composition is to stagger everyone's head position (but keep them close). Arrange faces on different levels so that any pattern of height does not distract the viewer from seeing the group as being one cohesive unit.
4. Position each individual so that they are actually connected to another individual. You can do this by having them stand very close to one another and better yet, have them touch another person. No matter the poses you go for, always try to incorporate direct contact through touch. Hands on shoulders, arms around waists, any way that you can get everyone in physical contact with each other. This will convey emotional closeness.
5. The other posing technique that I often use is to have the pose wider at the base and narrows at the top. Some photographers refer to this as the pyramid pose. This makes the group look like a single unit and the composition looks complete.
6. Pay attention to your subjects hands. It is usually a mistake to have everyone in your pose doing the same exact thing with their hands. Occidentally I will direct one or more of my clients to change their hand position to improve the pose as well.
7. It's ideal to have everyone in the family looking in the same direction, but that does not need to be in your direction. You can direct everyone to look behind you or at the youngest family member.
So it really does not have to be stressful the next time you want to capture your family's portraits. Be patient, be flexible and make it fun. You'll end up with some awesome portraits, lots of real moments, happy parents and happy kids! Try it out! It will definitely improve your photos.