Welcome to Disney with small kiddos!
First stroller: It seems this will not be your last trip with you little one, so I will buy a Citi Mini. If you buy it on sale at albee baby it will cost you about the same as renting it 2-3 times. The Citi mini is a great travel stroller, I finally caved in and bought one. I used to have an umbrella stroller for travel, gosh I wish I had bought the citi mini from the get go
The difference with the GT is not only that is has 3 wheels instead of 4, it is also lighter. The citi mini will make the cutoff for weight for AA and the GT will not.
Definitely ship baby needs to your resort: diapers, wipes, baby food pouches, etc. I always use
amazon.
Cleaning bottles: Oxo tot travel drying rack with brush plus travel size bottle of dapple
Backpack: plain black fisher-price diaper backpack I got at target for dad to carry, super cheap and useful.
Definitely bring a carrier. If you are only going to use it for lines a ring sling will do and you can easily store it your backpack. An ergo takes a lot of room, so don't bring one unless you are going to baby wear a lot.
Pack individual outfits in ziplock bags.
Do not forget to bring baggies for soiled diapers! I personally hate those that leave the poopy diaper in the bathroom trash as is, which then makes the whole bathroom stinky
They are also great for soiled clothes.
Great for lines: baby mum mums
Bring a sippy cup for water, straws are not allowed at AK.
I personally prefer touring 1/2 days with small ones, with the option of coming back later (which we usually don't do)
Rope drop works well as most LO are early risers, then an early lunch ADR and call it a day (character meals are great instead of meet and greets). Sometimes just late afternoon.
Fireworks may not happen this trip unless you have a baby that is fine sleeping in the stroller in the park late at night.
most of all have fun making your first Disney memories!