Kelly, I think you got your question answered for the most part but just to specifically answer your question, a life insurance policy is completely different from a will. IN a will, you can leave your personal possessions, money in your bank account, money in stocks.... to whoever you designate. A life insurance policy is money that isn't yours per se (but you pay a premium for) and upon your death, the amount you have previously choosen, is paid to whoever you designate.
Mark's policy is set up to pay 100% to me. But in the event I am not alive either, 50% goes to my parents and 50% to his parents. Then if his parents or my parents aren't alive it goes to his brother... Mine is set up the same, to pay 100% to him, then 50% to my parents, 50% to his... and so on.
I would HIGHLY recommend to ALL parents to get life insurance on your child. It isn't so much that if something happens to them you get the money, but rather as others have said, when they turn 18 you can turn that policy over to them. It's much easier to get it with a child (even one with CF, there ARE companies, I know state farm is one-or at least they use to) than for an adult.
Em, Mark's had the policy since he was about 15/16 years old. I just pulled out our policy, it's actually $23 a month for him and $16 a month for me (sorry). I know it would be more expensive if we didn't have our car insurance and homeowners through them (I imagine probably like $40 a month or so), but we get a line discount and a multiple policy discount.