I wish I had started running when I was that young. You'll probably have better luck getting him to run places with you rather than just going out for a run. If you have to go somewhere anyways, its fun to run barefoot there, but I'm not sure kids really get running just to run. Especially when they're distracted (which is of course always). Just a suggestion, ask him to run with you to the store or something. And probably don't show his friends your feet, haha.
I have to say that jumping randomly is really fun for some reason, I do it sometimes on my runs, when no-ones looking of course.
Thats really cool that people reacted that way, though I think theres something really joyful about seeing barefoot kids running and jumping. I thought so even before I started running barefoot.