Hi Jamie - I'm not sure what rentals you're talking about either, but I will chime in to say that I know of loads of 5-year-olds who still ride around in strollers here in Manhattan. It's odd elsewhere, but we don't have cars here and we need to walk a lot. Strollers allow the parents to travel further, faster, and longer, and to tow significant shopping along, too. People can agree that this is practical or can say it's appalling; I don't have children or a vested interest in the topic...my point is that, if you choose to put your newly-turned 5-year-old in a stroller for your Manhattan trip, you'll just be one of the crowd. And I know children several months older than your son who are not yet collapsing their strollers (although they're not in little travel cheapies, since they live here). Good luck and enjoy his birthday celebration!