The simple solution is for each of you to execute a power of attorney & delegation of parental authority to the other. In Colorado this will need to be renewed annually. Strictly speaking there is no basis or need for a third party to become a legal guardian of a child because that would normally "replace" the natural guardian (i.e. the parent). You might be able to get a court to appoint each of you as a "contingent" guardian or a "co-guardian" but the cost of two separate court cases might not be worth the effort.
Answered on Jan 14th, 2013 at 3:43 PM