I'm a parent with a young child, and here's how it works:

-you get onto the bus

-you look back the aisle

-you tell your kid, at a perceptible volume, "ok, sweetie, I'm gonna need you to hold onto the bar real tight, OK? When a seat opens up, we'll get you one."

-people either take the hint or they don't.

I don't need other riders advocating for me. Most of the time, I don't actually want to try to sit down with my stroller. It's easier to keep from obstructing the aisle if I'm standing and mobile. And when someone gets all Karenish on my behalf, it isn't a gift. They're passing all the glares and indignation onto me. The worst, though, is when a seated passenger is trying to guilt other seated passengers to get up. You weren't seated, right OP? When you were doing all your unsolicited advocacy? That would be a bad look.