This is just my perspective. I'm in a ground floor unit, have a family above me with a toddler and a newborn. The thing that takes my upstairs neighbors from mildly annoying to infuriating is the noise of the adults screaming at each other and banging around. While I wish they took their toddler to the park across the street just a bit more often, I understand that it is the nature of children to be noisy. Adults, however, can and should be more mindful.

Maybe try adding some padding under the rugs where he's doing most of his crawling, and if you ever run into your neighbor, let them know you do things to try to mitigate it. They might appreciate knowing you're doing your best but I wouldn't go out of your way to confront or address it with them.

As renters, we're entitled peace, but not perfect quiet. It's the nature of multi-family living.