Hello Amanda! Welcome to the Disney Parks Moms Panel.
When I travel with my little ones one of the things that becomes difficult is managing transportation other than using the wonderful
Resort Transportation offered by Walt Disney World Resort.
During early morning
Advanced Dining Reservations,
Special Events or Tours or trying to expedite Resort Hotel to Resort Hotel travel, I find myself looking into options with Taxis and Rental Cars but due to the diminutive size of my little ones the difficulty becomes: what to do with the booster seats?
Well Amanda, I found the smallest portable booster seats from a third-party vendor that I could(some even fit into backpacks!) and take advantage of the
lockers located at the 4 Theme Parks and 2 Water Parks located near the main gates of each park (as well as International Gateway for Epcot).
There are two sizes of lockers:
Small - 11" X 9" x 16" at a cost of $8 per day plus a $5 key deposit; and, Large - 17.5" x 12" x 16" at a cost of $10 per day plus a $5 key deposit.
The Large sized lockers appear to be pretty roomy, however I recommend you measure your booster seats while at home to be sure they will fit.
Happy Travels!
~Todd