Geocaching adventures in history bring families together because there are so many elements to it that your children, with their different gifts and strengths, will bring to bear their own special skills for the task. Solving puzzles and riddles, seeing through the camouflage, working the GPS device, or keeping things light with a self-professed, killer sense of humor (my strong suit) are all examples of this multi-faceted activity.
Another important point is the fact that their learning might go unnoticed since treasure hunting will likely trump that is a plus. But be happy that these particular pieces of technological gadgetry are prompting the kids to move about outside instead of sitting in front of the TV like a zombie. This is, of course, equally enjoyable for history buffs with no kids as well. Since trading trinkets is part and parcel with this activity you might want to read this informative piece entitled Fun and Interesting Geocache Swag Ideas so you can please the next cacher who opens the container.