Family portraits are a valuable memory for the future and you should actually take one every year. Having said that, I hardly have any family portraits of my own family because I am always the one taking the photos. Luckily making your own family portrait is not too difficult if you have the right equipment and know something about light and composition. I like family portraits which are taken outside, rather than in a studio. This can be a bit challenging because of changing weather and other people who might be wondering around while you are trying to take some family shots. I therefore advise you to walk around, find a spot that is quite, so that you do not feel rushed. Fallen trees are excellent attributes for family shots. Children love climbing old fallen trees and they are very good for composing your shot. I brought 2 tripods, which may seem a bit of an overkill, but you actually do need them. One is needed to place your camera on (this time you need to be in the shot, so you can not hold the camera yourself). The other one I used for an off camera flash, which creates a nice catch light in people's eyes and fills shadows. One of the downsides of taking family shots yourself is that it is difficult to take multiple shots, which is often needed for a good "all smile" result.
The picture on the right is a shot of my own family, taken with the timer on a Canon 7d, which was mounted on a sturdy tripod. The second tripod was positioned about 1.5 in front of me at about 2 o'clock.
The video below is of a group I photograped a couple of days ago.