We did 1 day at MK last year with our 2.5 year old DD. Because we only had one day, we stayed at the park ALL day and she just napped in the stroller. It worked out well. Our general plan was:
8:00am - Pre park opening ADR at BOG. Highly recommend this. It was so relaxing to walk down an empty Main Street and put us in great position @ Fantasyland before the mass horde of Rope Droppers descended upon us
8:50 - 11:00am - We did: Meet Cinderella/Rapunzel, Small World, Buzz Lightyear, Barnstomer, Dumbo (x2). In retrospect I would have skipped Buzz (she didn't get it) and done Winnie the Pooh instead
11:00-11:30 - We went to get her first haircut at the Barber Shop on Main St. This was wonderful especially because it was starting to get busy. They were so good with her, she got pixie dust, Mickey ears, certificate and a keepsake of her hair for only $20!
11:30-12:00 - we walked around Main St and through Adventureland to get a Dole Whip
12:00 - 1:30 - We stared using our Fp+s at Splash and Big Thunder. We split up our FP using Rider Swap (we were there with my parents). My daughter fell asleep at this point, but the original plan was for her to play at playground by Splash while we did those rides.
1:30-3:00 - ADR at Liberty Tree. This was great timing and location for the Festival of Fantasy Parade
3:00-3:30 - Parade
3:30 - meet Anna/Elsa FP+
4:00-6:00 - It was hot and crowded so we did People Mover, Carasoul of Progress, Philarmagic, and the Carasoul (x2).
6:00 - adults did Seven Dwarves Fp+ while my mom took DD back on Dumbo for the third time lol
After this we went to Enchanted Tales with Belle. The line was long but my DD loved it so it was worth it
7:30 - Dinner @ Pinnochio Haus
8:30 - We then got a 4th FP for Under the Sea. She loved it. After that, my parents took DD back to the hotel while DH and I stayed for MSEP, Wishes and one more ride on BTMRR (we had a leftover Rider Swap pass).
Sorry for the novel... I was surprised at how much we got accomplished in one day and how much fun DD had! Have a great trip!!