E.A.
I'm a redhead and all of my kids have blonde hair and blue eyes, so I feel your pain. It's ok to let him get a little color, it's ok for him to be exposed to the sun. You just don't want him to burn, that's what damages the skin, not the tanning.
Keep him out of direct sunlight during the worst of it, 10am-3pm, but otherwise he should be fine. You want the melanin in his skin to show up, it's protecting him, you also want the sun to get to his skin, he needs it to make Vitamin D. Have him wear a hat and keep his shoulders covered, that will reduce the risks the most.