I am frequently asked this question. In California we never deal with Social Security in the Marital Settlement Agreement because the concept is pretty much understood under Federal Law. If you have been married for at least ten years, your spouse will get derivative benefits. Period. They can do the math and decide whether the derivative benefits are better for them or not, but they get the choice. Not you.
But have no fear, derivative benefits have no effect on your own benefits, so quit worrying about it anyway and spend your energy on golfing once you retire. 😉
Here is the CNN Personal Finance Help Desk article on the subject.