I used a free online image editing app called Pixlr to achieve this effect, but you can do much the same thing in other software, such as Photoshop or GIMP.
Of course, you don't need to use family photos. We'll even discuss how to insert your family members into exciting action scenes or far-flung landscapes. It's your coloring book, so you can choose the story! Even better, why not let the kids decide?
I'm going to talk through this process in a lot of detail, but that's only so that a complete beginner will feel comfortable. Don't be intimidated by the number of steps; you can actually complete the project in about 5 minutes!
Step 1: Choose a photo
If you're planning to edit any of the people in your photo onto another background, it helps if the original photo is taken against a fairly plain background. For example, you could start by photographing your kids fiercely brandishing toy swords in front of a blank wall, then edit them onto a pirate ship background later!
Save whichever photos you want to use to an easy-to-find file on your computer.