DH and I will be at YC on almost the exact dates as y'all! We'll be on the lookout. First time at YC for us and I'm excited. I don't know if it's encouraged, but we've definitely seen scooters being charged in the hallways at WL, AKL, and Boardwalk. When DH and DS2 each had to use one due to injury or surgery- once at POFQ and once at CSR- the
scooter fit fine in the room even with 3-4 of us and those were moderate rooms.
Nice score on the king room! I was out of town at training the first part of this week and when I checked in Sunday I was asked if I had a floor or location preference. I said no and then I was upgraded to a king suite! Hey, it was just a Holiday Inn, but it felt like some pixie dust to me! I bet you're right though- they'd rather give the king rooms to solo travelers. Enjoy your vacation!
I would pick YC because it's something new. I struggled to pick between the 2 as well but decided on YC for DH and I because I can see doing BC in the future with our kids, plus I wanted the guaranteed balcony for us. We used it every night on our just the two of us trip, while on the last trip with the boys and their GF's we hardly used it. Maybe you could bring some small things to "decorate" the balcony area for her birthday too.