Make sure you are very specific with respect to your kids. My wife and I had one drawn up; I am an attorney, tho not in wills, and went to someone who does this for a living.
Ours read specifically that my folks are in charge of our son's money (in trust), her folks have custody. We specified vacations to see my folks (in Buffalo), type of school we wanted our son to go to (private, Catholic etc.), specific years that he would get disbursements etc.
It may seem ridiculous, but try to think of every possibility. Remember, this is the place to put down all of your wishes and desires as to how your kids are raised in very detailed specifics.