The will of Adam Yauch of the Beastie Boys illustrates how not to designate a guardian for minor children.  Apparently, he and his wife could not agree on the guardian for their then 3 year old daughter, Tenzin Losel, when they executed their wills in 2001.  They compromised and designated his parents if he died in an even numbered year and designated her parents if he died in an odd numbered year.

Several points.  Unless the parents of my clients are very young, I do not recommend that the clients designate parents as guardians. Second, clients should re-visit their guardian designation regularly and adjust it accordingly based on life changes, especially if a client has a terminal illness.  Third,  unless the child is a Sherpa, I am not sure that Tenzin is a good name.