Greetings Melanie!
How exciting to be planning a trip to the Happiest Place on Earth!
As you may know, lockers are one of the many
Guest Services offered at the Disneyland Resort.
They're available for different prices, depending on the size of the locker.
Locker rentals inside the
Disneyland Park and
Disney California Adventure Park are available for $7 and $10.
The larger lockers (ones that would be big enough to store a booster seat) can be rented right outside of the Parks' main entrances, where they're available for $7, $10, $11, $12 and $15.
The size of the large rentable locker is 18" wide x 25" high x 37" deep.
I've never seen the
lockers completely sell out, especially if you arrive early but it is possible so I would suggest you plan accordingly.
Another idea to avoid having to carry around the booster seat is to take the Anaheim Resort Transit Bus. Depending on which hotel you're staying at, this quick bus ride to the
Disneyland Resort is convenient, affordable and it eliminates the need of carrying a car seat.
I hope this help.
Have a Magical vacation.
Sending you Faith, Trust & Pixie Dust!
-Anabel M.