Pick up some inexpensive items from a dollar store to use for "special awards" that you create while on the trip. These retail stores have other games and sets that are excellent for in-car entertainment.
Hold back some of the "treasures" you have to be used in emergencies only that can cheer someone up quickly. Children can be quite useful in setting up and striking camp.
Children should be assigned to different tasks. What is also known is kids need frequent stops. An RV resort or campground with a swimming pool and playground area is something the children can look forward to.
Keeping children active along the way is worth any time that you may spend preplanning activities. Take the time to pre-plan as much as possible because when the time comes, and it will with kids when they say Im bored, you will have options.
The kids may, in the beginning, crab about not having all the usual amenities at home but after just a few fun experiences, that will fade away and they will have lifetime memories to fall back on forever. Keep it FUN!