I read this post on photographing your family over at TUAW—a website I enjoy. The article, I did not.
The article suggests that taking pictures of family, and especially young children, is difficult. So difficult, in fact, that the only way to deal with is to "Get them to Pose." The problem is untrue, and the advice is bad.
(Although the article was written in the context of photographing children, the concepts discussed here apply to any people with whom you are close, regardless of their age or relationship.)
The problem with posing is that it has the whole process backwards.
Worse still, if the people closest to you are willing to pose, you are not only losing the opportunity to capture those intimate and meaningful moments, but you are also missing out on practicing your craft.
The simple rule is: no posing. Ever. Ever. Outside of a commercial photo shoot, posing photographs is not only insulting to the subject, but it means you're not observing. The most fundamental part of being a photographer is to see what's going on, and to capture it. Creating a moment by posing people or arranging a situation means you aren't observing anything that's going on. Instead, you're interfering.
People are plenty interesting as they are. The most interesting aspects of people are revealed in what they do and how they look when they're engaged in something meaningful to them.
Posing someone for a picture removes all the humanity and strips the person down to a mere superficial object. It's basically saying that you find nothing possibly interesting visually about them. That's about as insulting as it can get. And this is the reason why even professional photographs of models usually have no emotion in them. (The same is true in portrait paintings.)
The only necessary step to correcting this atrocious habit is to stop doing it. Simply, never ask anyone to pose and do not take a photograph if someone poses. For the people closest around you, such as your family and friends, they will adjust rapidly. The more often you use a camera, the more relaxed they will become. You will start to fade into the background and they will stop caring about what they look like so much. (If you are a parent or a significant other who can assert such control, it also helps to start eliminating bright white and garish patterns as a wardrobe choice. The people you care about will not only look more attractive in the photographs you take, they will also have a better fashion sense.)
Moreover, you'll start seeing more pictures. By putting your attention on your involvement in what's happening, instead of trying to think how to arrange people, you'll see more interesting moments. By participating and observing, you'll have more empathy with those around you, which will help you to anticipate meaningful moments.
Further still, you'll develop the patterns of observation and empathy which will help you to take better photographs of everyone—not just people you know.
But back to why we pose. The temptation to take a posed photograph isn't always about laziness. Sometimes it's a genuine difficulty with being able to read a scene—to find our place in the action, to find our perspective. The pressure to capture a moment in what seems to be an important event produces anxiety. That pressure doesn't feel good, and one way out is to gather up the relevant players and take a group photo. It's understandable, it's common, and it's a mistake.
Posed pictures are almost universally bad because of what they represent: a false moment. People don't naturally gather in ordered groups and wear forced smiles for an extended period of time. And if they do, they aren't happy about it. No one really likes to pose, and it shows. The group picture is a kind of proof picture: "see, we really all were in the same place at the same time." It seems like evidence. Evidence that can't be used for anything good.
It's true that it will be difficult, if not impossible, to capture a legitimate moment among more than a few people. That's not a bad thing, however. Too many relevant people in a picture makes it seem like Where's Waldo instead of an interesting moment. Finding the patterns in relationships is a worthwhile venture, and it's worth documenting. Ultimately, your audience will be more grateful for interesting pictures that contain an understandable moment with a small number of people than a wide shot of a group whose faces can barely be perceived.
If you are finding it difficult to take pictures of kids because they are "too active" or seemingly too chaotic, that's not the problem. The problem is that you aren't orienting and positioning yourself. The answer (as always) is to take a step back. Observe what's going on. See the patterns in what people are doing. Position yourself appropriately and do what photographers do most of the time: wait. Wait for things to come together into something interesting, and then do your job and capture it.
Part of that waiting, however, can be involving yourself in the event. By participating in the action, you will more quickly get a grasp of what's going on and the timing of things, and you will therefore find it easier to predict when the interesting bits will occur. It's not always easy (or even acceptable) to participate in the action, but it certainly is both easy and acceptable when the action involves your friends and family. As a bonus, the more you practice with the people closest to you, the easier it will be to understand the patterns and the unfolding action in any context. Practice is the key, and it's a crime to waste the opportunity of practicing with the people closest to you.