This is wasting your time. Madison could have an accident at any moment. You walk down to the steps and pick up one of the packages. Madison's mom is there, watching you nervously; trying to reconcile her approval of you in general, with her disapproval of your strange behavior.
As you go up the steps, you make eye contact with Madison's dad again, and say,
~You are completely okay with me putting Madison in diapers~
Andrew's standoffish pose relaxed; his heart-rate slowed to normal.
"...shit." He says. "I'm really sorry Daniel, I don't know why I was being weird about this." He steps to the side. "Here, you can put Madison in a diaper if you want."
You nod, thank him, and go up the steps onto the 2nd floor, just as Alex goes onto the steps behind you.
"Andrew...what are you doing?" She asks, perturbed but mostly confused. "Why are you letting Daniel do this?"
"Look sweetie, it's no big deal. Everything will be fine." He takes hold of her hands affectionately.
"....you really think it's okay?" Alex asks him, looking over at you.
"Of course. I have complete faith in Daniel."
At that moment, Madison came out her door, because she had heard her name mentioned a few times. She just stand there, looking at the strange staircase scene going on.