In my diaper bag I carry
5 diapers,
small pop top wipes container,
former poncho (that ripped beyond repair) which has been trimmed down to become a "Disney Themed" liner for changing stations,
Cloth diaper that I use as a head cushion during changes, burp cloth, and general mess cleaner,
2 toys: Discovery's Super Yummy Teether and a cloth book about Pooh
spray hand disinfectant
Clorox wipes in a ziplock bag
I also have a couple baby food jars, 2 baby spoons, and a Munchkin fresh food feeder, a mesh "pacifier styled" tool that allows baby to suck and chew on foods without fear of small pieces choking her.
Onesie and a Mommy sized T-shirt in a gallon ziplock bag. This allows for one really messy disaster clothes change and a place to put the really messy clothes.
Maya Wrap, a double ring sling, which allows for comfortably carrying baby in long lines and onto rides.
Small wallet/cell phone holder.
That is it.
It all fits in a rather small diaper bag with room left over.
For a trip to Disney I would add:
super small pancho packs from Wal Mart
First Aid kit with Moleskin, pre-cut, bandaids, small neosporin, a few doses of tylenol, sunscreen, and an extra tampon.
I hope that helps. When I was a first time mom I tended to carry everything, but over time, I have cut back on what I carry due to my parenting style and life experiences.
I would suggest you lay out all your itmes and ask yourself, is there a way to make this smaller, or have an item do double duty? For me, I used to carry the changing pad that came with the big bag, but decided it took up too much space, wasn't soft enough for the little one's head, and could be replaced by one vinyl sheet and the cloth diaper I was already carrying.
I also used to carry way too many diapers and ointments. In my situation, my kiddos rarely have diaper rashes, so why was I carrying baby lotion and butt paste everywhere I went? For a long trip, like Disney, I would bring baby lotion and butt paste, but I would leave them in the hotel.
Oh, some little ones really love their sippy cups, but my kids went from the breast to a small cup with a lid and straw. Animal Kingdom doesn't have staws, so I would add a sippy cup for that park.
Have fun!