Hi there, Nery! Thanks for bringing your question to the Disney Parks Moms Panel!
I always have a small purse and a backpack with me whenever I visit the parks. I just can't seem to live without my water bottle, snacks, portable phone charger, and other necessities when I'm out for a day of fun. So I'm happy to report that you can most certainly bring along your mini backpack when you visit the Disneyland Resort. It will be subject to search, so be prepared to open all the pockets and remove any bulky items so security can properly inspect it. You can then take the bag with you everywhere, including on attractions.
For most attractions, you will simply place it at your feet or in a small pouch in the ride vehicle if it's small enough. If you intend to ride
Grizzly River Run, I suggest storing it in a nearby locker while you ride as you and any belongings you take with you will get soaked. The lockers right by the attraction are free to use while you ride. If you find that you would rather not carry around anything while in the parks, you can
rent a locker for the day in either theme park or in the esplanade area between the two parks.
I hope this helps. Have a fabulous time at the Disneyland Resort!
-Linda