Do My Wife and I need to agree on Secondary Guardian

It depends.  The guardianship provision is normally effective when both parents die at or about the same time.  As an example, if the husband’s will nominates his parents and the wife’s nominates her parents and both husband and wife die at or about the same time, then the court will have to decide who is the proper party to be the children’s guardian.  That will cause undue hardship on all parties concerned as well as considerable unnecessary expense, a large part of which your estate will have to pay.  On the other hand, if the parties dies several years apart from one another, the guardianship clause in the second will to be probated is the only one that would be effective, so there would really be no conflict between the two wills if different secondary guardians were chosen by the husband and wife.