When he was 11, I took my younger son on a 3-day trip. He already had the gear, since the bike was my only transportation at the time. Anytime we went anywhere, we took the bike and it had been that way since he was seven so he had lots of pillion experience, and was comfortable enough to fall asleep on the middle of my back on the way to karate practice every afternoon. This trip was also the shakedown run for my new Harbor Freight trailer and the HitchDoc hitch on my C10.
Day 1 took us 350 miles up I-75 from Tampa to Americus, GA where we got a hotel room and a pizza and then went to cruise through Jimmy Carter's town of Plains. It really is so small you could throw a rock from end to end. The next day we toured the Andersonville Civil War Prison Site and its spectacular
National Prisoner of War Museum - the very best single-issue museum I have EVER experienced - then took the back roads about 200 miles to the Steven Foster State Park where we camped for the night. It was his first time camping and he loved it. In the morning, 70 miles of backroads took us to I-75 and another 150 miles home.
He had a great time. We were even chatting about it a couple of months ago as we went through the pictures; he's 21 now and finishing up an Education degree at USF. The trailer was great too.
Take reasonable precautions and everything will be fine. Remember to stop more often than you need to; a kid will find wonder even at a highway rest area if he's in the right frame of mind. Let him pick the food and stop to see anything he expresses an interest in. Get little things like refrigerator magnets. Take pictures. Take the time to talk. I'd say you should do it; it'll make memories that'll last a lifetime.