Greetings, Heather!
Thanks for bringing your great question to the Disney Parks Moms Panel. As a mother of a preschooler, it wasn't that long ago that I was in your exact position wondering where I could get whole milk for my toddler in the parks.
Since many young babies and toddlers are just like your daughter, you are definitely not alone. I have seen whole milk available in Disneyland Resort Hotel gift shops before heading to the parks. In the Downtown Disney District and in both Disneyland Park and Disney California Adventure Park, my go-to spots for whole milk are actually the Starbucks locations here. I have seen whole milk sold in sealed bottles, but I have also just ordered a "tall" or "grande" whole milk from behind the counter which was sufficient. To keep milk fresh throughout the day I brought a very small cooler with ice packs to store in a
locker rental location in the parks. I have also grabbed complimentary ice cups from Quick Service restaurants to keep milk cold on a warm day. If you need to warm your bottles, or if you just want some privacy during changing or feeding, head to the
Baby Care Centers in Disneyland Park and Disney California Adventure Park.
Did you know that little ones can ride any attraction that does not have a posted height requirement? Your 18 month old child might also even be tall enough for some 32" height requirement attractions like Luigi's Rollickin' Roadsters, Mater's Junkyard Jamboree, and Autopia. She's going to have such a blast!
I hope this helps, and have a magical day!
-Jennifer