Coloring books generally have a theme of sorts. It might be that they are based on a Disney movie, or it is about animals, or vehicles, or something else. When selecting books for your children, remember that they will want to express their creativity, and will have a lot of fun with any coloring book, but will be more interested in a coloring booklet with a theme that appeals to them. Choose a color book that features their favorite characters, or the item of interest in their life. For example, if your little boy just loves trains, get a Thomas the Train coloring book. If your little girl is as girly as they come, look for the Disney Princess coloring book, or possibly Strawberry Shortcake.
Often at times, the trip starts at the airport with excited and maybe nervous children preparing for what may be their first time on an airplane. Thankfully, most airlines will allow pre-boarding for families with young children to avoid the crush of the regular boarding call. Arriving at the airport in plenty of time to familiarize your children with the airport processes will help and will allow also allow them some time to explore the airport. Regardless of if you are traveling by air or by car, always remember to pack snacks, drinks, books and other attention holders to avoid the dreaded, "Im bored" complaints. An extra change of clothes also helps in the event of any travel related illnesses.
You have a greater tool - your PC - that can be helpful to get the printouts of diverse colorful sheets. Guide the children, exclusively during the holidays to add illustrations to the colorful-page, and showcase them around the prominent places of the house. This will give them, a sense of pride and joy for their creativity, and would lead to further productive pursuits. Thus, you will witness that there are massive advantages of coloring-page relatively to coloring books. Coloring sheet are economical, costing you only a couple of cents in ink and paper rather than a few dollars for a coloring book.