I was never even thinking that I'd be able to keep the strollers open. I was worried if there would be room for them folded, so the fact that you're even considering a scenario where they could stay open makes me feel better! It's possible that I'm imagining this space as much smaller than it actually is.
I keep going back and forth on the 2nd stroller. While we won't need it 90% of the time, I really think I'm going to want it for that walk to and from the parks from the hotel/bus. All of the night entertainment is after their bed time, so if I want to try to see any of the fireworks, I need to be realistic about the fact that I'll have very tired children getting out of the parks on those nights. We're going to get the smallest umbrella we can that can hold their weight (they're only 31-33lb right now, so something that goes up to 40 will be fine). We are planning on using it to get in and out of the park but otherwise keep it folded attached to the double jogger handle throughout the day.
The closet door won't work for door hanging things, but the bathroom door could, right? Regardless, the more spacious of the hanging things I have are actually designed to go in the closet, either on a hanger or over the top railing, not over the door.