My DD was almost 8 months last year (I was pregnant with her on our first trip!). The Ergo carrier was a lifesaver. I was BFing, so I just fed her whenever she needed to eat, and she napped in the carrier as she wanted to. She was also on solids 2x a day, so I brought some jarred food with us as well as puffs and sippy cups for water.
A hat is a good thing to bring in case it gets sunny.
I took her -- in the Ergo -- on most rides. I'd take her out for the shows if she wasn't sleeping. I let her get down where I could -- in line for the princesses, before our dinner reservations at 1900 PF in the lobby of the GF, etc. Just to give her a sense of a little freedom. My older DD was 4 last year & she used the stroller most of the days, but sometimes we'd kick her out to give my back a break. The baby was happier on me though.
The baby care centers were never nearby when I could have used them ... but we survived just fine without them!!
Take extra clothes (even an extra shirt for you) and lots of wipes, just in case! We had a few blowout diapers on our first few days there.
Don't forget to bring some infant tylenol just in case -- never know when teething pain will pop up at that age!
It was a blast. She loved the characters, napped easily on me (though for short spurts), had fun on the rides. She LOVED Small World. Seeing her face light up when she saw all those "babies" was just priceless!!! HAVE FUN!