Thanks again to everyone for their thoughts and suggestions on this!!
Reporting back, my 10-year-old and I had an awesome experience (11-1 AM at MK on 4/27).
My 7-year-old hit a wall that night around 9.30 pm, so she and DH headed back to WL while DS10 and I stayed on. (Someone commented that 10 is roughly the age when kids build more stamina for this sort of thing, and based on our experience they nailed it).
I needed a break/snack before we launched into attractions, so we spent a little time after the park officially closed at 11 PM relaxing in a garden in the hub and looking at the castle (the special lighting for the 50th is so beautiful
. People were streaming out of the park, and most attractions were walk-on by the time we got going again. We went straight to Haunted Mansion; it was just us and a few other people, and was genuinely creepy in this context!! So much so that DS refused to go on Pirates next, which I think would have been really fun (oh well. . ).
We quickly hit a few other attractions, and then went to Fantasyland for PP and Mine Train, which both had short waits. We adore the PP queue, and were happy to spend a little time on line in the nursery scene. The line moved quickly both at PP and Mine Train, which was a welcome change from regular hours when the line stops frequently for
genie+, etc.
We got off Mine Train around 12.45 AM; my son wanted to squeeze in another attraction, but I was totally done at that point. We slowly made our way down a nearly empty Main Street, which itself was so memorable. I was about to take a selfie of us in front of a clock (to document our late night), and a cast member immediately offered to take it for us
.
So getting back to the topic of kids and very late extended evening hours. . . honestly, I think I knew my 7-year-old wouldn't be up for it, and thankfully my husband was happy to head back with her. However, my 10-year-old was 100% game, and we had such a memorable night together. I'd say if you're lucky enough to be traveling with 2 adults, be prepared to split-up depending on how each kid is doing.