My suggestions (most gathered from here) from our recent trip with a 10m old are:
1. Bring a cheap plastic shower curtain liner (dark in color) and a few of those 3M clips for the wall that can be pulled off. You can then create a little "room" for the pack and play in your hotel (we did this in a corner of the room), so the little one can sleep without seeing everyone.
2. Bring a baby Bjorn (carrier), for the ride lines and rides, if she can fit in it still. (we felt a lot safer with her in it while on rides (small world, peter pan, jungle cruise etc.) than loose and able to crawl around.
3. Bring a towel into the park. You can drap it over your stroller and block out some of the commotion if she can nap in her stroller.
4. Take a break EVERYDAY for a nap back at your hotel (esp. easier if you are on property). Everyone is then refreshed and can stay out a bit later.
5. Bring a lot of snacks for the lines (puffy's, cherrios, crackers)...just be careful so they don't all end up on the ground for everyone else to step on.
6. If your stroller doesn't have a rain cover, bring an extra rain slicker for it (target has them for just a few $ in the travel & sporting areas).
7. Bring your own stroller. The parks rent them, but they are not too good for little ones. (they are really $$ too).
8. Use the baby care centers. They are great for feeding/diapering/ or resting. (they also have toys for older siblings)
9. Use the Baby Swap at all rides they allow. This feature allows 1 parent to ride (with other children/people in party), then non riding parent gets to go on ride through fast pass line when the riding parent returns (up to 2 people get to join them too-- so it is fun for other siblings to ride 2x).
10. Bring music to play in your hotel room and or run heating/aircond fan to create white noise while the little one is sleeping and you are still awake. (we brought our IPOD with speakers and put it under the pack and play, playing Disney Music of course

)
11. Most importantly enjoy your self and slow down!