I've used the buses holding sleeping children many times (my own when they were younger, and nieces, nephews, cousins, etc over the years). Each time I made the decision to walk onto those crowded buses, knowing I could be standing for 30 minutes with a child in my arms, I took full responsibility for that decision. I have never had the nerve to feel entitled to someone else's seat when they've been waiting in line longer than I have, regardless of how able-bodied they are and how uncomfortable I am. In fact, anytime I've gone on a bus with a sleeping child in my arms I have purposely avoided looking at the people in the seats, because I don't want them to feel obligated to give up their seat for me. They were there first, they can have their seat! Sometimes people have insisted on giving up their seat for me (if I have a sleeping kid) because they are chivalrous and kind-hearted. I always show plenty of gratitude because they were not under any obligation at all to do that for me. I am capable of waiting for the next bus, I am capable of exiting the park during a time when the buses are half empty, and I am also capable of calling a cab. If I make the decision to enter a crowded bus during the busiest time of the night with a sleeping kid, then that's on me!
I find it annoying when other people who make the decision to enter a crowded bus feel that the people who were lucky enough to get seats should have to pay the price for their poor choice and stand up on their behalf. That "entitlement" attitude drives me insane.
One demographic I would gladly hand my seat over to is a young, tired kid. They didn't make the choice to stay in the parks all day long, and they didn't make the choice to walk onto a packed bus. That was the result of their parents' poor planning, and I'm not going to hold them accountable for that. They can have my seat.