Your kids, on your bike? There is a short answer, but it probably ain't politically expedient... sooo...
Don't know if this is helpful, but I give the kids in my neighborhood rides. Short little hops. Usuallly up to the school and back. We might go 20 mph tops. I usually start out thinking it will be one kid, one trip, turns into 6 kids, two trips apiece. I have my own little munchkin fan club. There was one Mom, and there was no way in the bad place she was letting her little spawn on that big scary bike. I am not one to push, but this kid WANTED a ride. I offered Mom a ride, with the idea that maybe she feared what she did not understand. Had to offer it three times, but she finally accepted. I really felt bad for her son, but to his credit, he was patient and cool. Took Mom for a little spin, and she came back smiling. Little dude got his ride. And he is usually at the front of the line now, with Mom's blessing. Story has a happy ending.
I call this little public service "Spreading the Sickness". I have met too many adults that are terrified of bikes. I have a half-dozen pre-teen kids in the neighborhood that are not gonna grow up terrified. Makes me happy. I have loved motorcycles as long as I can remember, because I got introduced to them by patient, cool people. When I have the chance to intro someone to motorcycles? Low key, slow little ride first.... then, when they feel comfortable? They will let you know.
Grandparents can be a delicate situation, but I think you have to find a way to make them "put up or shut up". Take them for a ride or at least offer it. If they are not willing to experience or evaluate your rig and your riding? Then they kinda have no credibility.
Hope it works out. Sharing a ride with a kid? Kind of a neat bond, providing the kid enjoys him'/her self. Good Luck!
Primitive and Useless, Archive from another time.