request that all members of Congress commit themselves to be Leaders of the Planet by pledging to do so.

By pledging to be a Leader of the Planet, members of Congress may then do whatever they think is appropriate to that commitment. They would simply say, in private, "I pledge (or commit myself) to be a Leader of the Planet," then live that obligation in their legislative and personal lives.
In addition, they could signal that intent by joining the Leaders of the Planet group on Facebook