Since I had made magnet boards for the kids, I wanted to maximize their potential for the many-day-long road trip. Here are the rest of our magnet activities:
Magnetic Children's Rhymes
Letter Game Markers:
here, here, and here) that would need some sort of discs to mark. They used their initial magnets for these games as well as to just play with.
Now that I'm typing it all out, I can't believe how much we had to do in the car. I will say that I didn't even open everything I had prepared for the kids. And I'll also say that, with a 4 and 2-year-old on a trip that had us in the car for over 35 hours total, we never had a single moment of frenzy. Both kids were entertained, happy, and pleasant the entire time which is still shocking to me. I'll be back with many more ideas!