I love 1 yo at Disney!
A few thoughts in addition to what’s been mentioned:
First hair cut at Harmony is our favorite 1st birthday memory with our son. You get a certificate, his little locks were wrapped up for me (with pixie dust optional ), and he got mouse ears and tons of stickers. It was super cute.
Boardwalk bakery will do a cake for you. I did one for breakfast delivered to our room. We had little party supplies and did “smash cake” pictures in the room instead of him being a mess at a restaurant. Immediate bath afterwards!
Our trip with our 1 yo was not as dramatically different than our prekid trips like I expected (3,4 etc is a different story).
We also did well planning really early dinners, keeping his bathtime on schedule, then putting him in his jammies and walking the boardwalk/Epcot for an evening drink! It’s a fun age to have them there!