Coloring books for adults is an offspring of art therapy which is a mental health profession that is the process of making and creating artwork which intends to "explore feelings, reconcile emotional conflicts, foster self-awareness, manage behavior and addictions, develop social skills, improve reality orientation, reduce anxiety and increase self-esteem" (according to the American Art Therapy Association). So basically, it's similar to good old therapy. Also, art therapy is not only about mental health and improving yourself - it's a form of personal expression, as well.
So prepare ahead of time and make sure that you've got enough distractions for the kids so that the trip will be uneventful in terms of fighting. Siblings don't usually like sharing stuff so you'll need at least two of everything. Two sets of crayons, two sets of coloring books. And it's probably best to make sure that both sets are exactly the same so that they don't get into an argument over the perception that Billy's coloring book is better than Casey's.
On the front, write: "I'm ready! I welcome to all my buddies! Share and enjoy my birthday with greater amusement and enjoyment!"
The themes of adult coloring books are usually intricate and centered more around adult images, not your childhood counterparts that included bunnies, super heroes, and farm animals. You would expect to see geometric patterns, psychedelic patterns reminiscent of doodle art type pages, fantasy images including angels, dragons, goddesses and mermaids, and ancient designs of religious and spiritual nature.
Characters that children love, like Pokemon, Dora, Barbie, Thomas the train, Scooby the Dog, Donald Duck etc and many more can be easily accessed and printed out for them to add their own imagination of colors. Coloring can be a family activity as well. It is one of the best ways to spend time creatively with your child and bond well. Thus you can spend a relaxing time that is a brain tonic for your child too!
Best of all of course are free pages that can be printed out at home any time you like. There is so much variety obtainable that as long as they have their pages and something to color with a child will never get bored. For many children, there is no greater gift they can give to Mom or Dad than a picture they coloured all by themselves. Inside or outside of the lines, any page coloured with love and happiness is a masterpiece.