Hi Juliet!
Thanks for bringing your question to the Disney Parks Moms Panel! With so much for little ones to experience and discover at the Disneyland Resort, it is a bare necessity for toddlers to get some rest during the day. I know that all children are unique, but I'll give you some tips that worked for my toddler on our last few visits.
My son is used to napping on-the-go in his stroller so we make sure to always bring our own stroller versus renting one. I also suggest a stroller that reclines so children can nap as comfortably as possible. There are so many peaceful areas in Disneyland Park, Disney California Adventure Park, and around the Disneyland Resort Hotels where we have taken our son to nap. Recently we enjoyed a funnel cake on the lower level seating area of the Hungry Bear Restaurant at Disneyland Park with a majestic view of the Rivers of America while my son slept peacefully in his stroller. We also love the serene sights and sounds of Grizzly Peak at Disney California Adventure Park. Sometimes when the grown-ups want a little rest and relaxation, we enjoy spending some time in the lobby of
Disney's Grand Californian Hotel & Spa. You can sit and have a beverage here while your little one sleeps to the calming Disney melodies played on the lobby piano.
If stroller naps aren't your granddaughter's favorite, I'd suggest taking her for a calming ride on the
Disneyland Railroad. Many times my son has been lulled to sleep in our laps. You can stay on these trains as long as you'd like for your little one to take an uninterrupted nap while you enjoy the scenery around Disneyland Park.
I hope some of these ideas work for your granddaughter, and have a magical day!
-Jennifer