So will be going to blizzard beach!
How tall is your niece? BB has numerous 48" height restrictions, just don't want you to be surprised or disappointed:
Summitt Plummitt, Slush Gusher and Downhill Double Dipper all have a 48" height restriction.
At Typhoon Lagoon the Crush 'n Gusher and Humunga Kowabunga have the same restriction.
As for your MK list, how can you skip Mickey and Minnie's Country Houses in Toontown? You'll meet both for photo ops at the end of your "tour". When you leave there jump on the Railroad, station just to your left as you exit.

Though she rides the big rollercoasters she may also want to try Goofy's Barnstormer, it is right across from the country houses so you can make that a spur of the moment decision. We took some great photos with Goofy and his son Max at the Barnstormer years ago. By the way, we found Toontown to be closed during evening EMH, so if that is still true you'll want to hit those during regular hours. Tiki room was a walk on during EMH. Aladdin was nice "substitute" for Dumbo during EMH too (long line for Dumbo).
Peter Pan is also a must do for us. Its even a Fastpass ride! Your niece will get a kick out of flying at WDW. I'm sentimental, the carousel is a must do.
I'm with wigd, Fantasyland first.
