help-understand Milleniums?

Barrbee, if your grandsons isn't into cars, then that might just be a non interesting thing for him. You could just pack up the whole lot of mags into a box and mail them off with a note that simply says, "Enjoy! I did. It's a great hobby. It helped save me tons of cash!"
Not hearing back from the family is another issue you will have to contend with. I recommend a in person visit. They yield the best results.