I work for a vet, and have owned my fair share of dogs off all varieties over the years. Cutting his fellas off now is not going to change his humping, it is a trait that has already set in. However, with that said, you can prevent the onset of other problems with the dog by having him neutered. It will reduce the risk of prostate problems, including cancer. You remove the possibility of testicular cancer, these are just the top two problems that can occur leaving an older dog intact.
As to solving the humping problem, you have to take the source away. Pen him up or tie him up, whenever the annoying kids come around.
I have male and female dogs that were spayed/neutered years ago, and they still hump one another, that is just a dominance thing.