Uh... I'm pretty cool with kids in the cabin, but I draw the line at changing a diaper at one's seat. That's disgusting. There's food and drink being consumed in the cabin. Would you feel comfortable eating and drinking within inches of strangers' urine and feces?

You can too change a kid in an a/c lav with no changing table provided. I changed my (then) five-month-old son in the tiny reaqr lav of a TW MD80, which took some doing. But I would never inflict this ultimate hygiene crime on fellow pax.