When I want to be in front of the camera with my kids I like to set up my camera on a tripod or other stable object. I then use my compact wireless remote controller (like the Canon RC-6 wireless remote) to fire off some shots while I pose and interact with my kids. I like to have it set to a two second delay so that I have time to hide the remote so it won't be seen in the pictures. To focus, I ask one of my darling children to stand/sit in the area where I want to be photographing. I then focus on them and usually mark the area where they are so I know where we need to be positioned. My camera is set to back button focus, so that my shutter button is not responsible for my autofocus. You can read more about back button focusing right here.
But if you don't want to do back button focusing, then just switch your lens from AF (autofocus) to MF (manual focus). This means that you can take photos, and your camera won't change where you originally focused. I try to set a slightly smaller aperture than I would typically do for portraits because I know that we will be moving, and I want to ensure that we are sharp. I want some room for error. If I shoot at f/1.4, the chances of me getting everyone in focus while firing remotely are not so hot. But if I shoot at f/5.6, I am more likely to ensure everyone is in focus. So, now I just fire away and try to get my kids to relax and be natural. The holiday card shared above in #9 was taken using a tripod and remote trigger.
If you have a camera with Wi-Fi capabilities, you have the exciting ability to use your smartphone to shoot remotely. First, ensure that your Wi-Fi is enabled on your camera. Then, with your smartphone, go to your Wi-Fi settings and connect to your camera. Then open the Canon Camera Connect App on your phone (or tablet), and choose "remote shooting." Here, you can see what your camera sees on the mobile device, change your settings, and take photos remotely. How cool is that???