Unwanted Nickname

I am absolutely in love with my son’s name, Camden James. His name holds a lot of importance to my husband and I, Camden is the place we got married. James is after our late coworker. I am so in love with his name that it never occurred to me that people would call him CJ. I am not a fan of people calling him CJ. I feel like it is completely impersonal and misses the significance of his name. My side of the family has respected my request on not using his initials. My husband’s family is not complying.

Any one else have this problem of unwanted nicknames? How do you tactfully handle something like this?