Lots of great suggestions here!
My kids are older now but I used to like to pre-buy some souvenir type toys that might be cheaper from the
Disney Store or wherever sells their favorite characters. I check the dollar spot at Target for little goodies, special snack treats or light up whirly toys. Anything to save some $$ instead of getting bombarded with impulse gimmies, lol. I liked to space the toy drops out throughout the trip like as a surprise when waking up or returning to the room.
For my purse I use a dangle hand sanitizer and a travel pack size of disinfectant wipes. Also a small battery pack for charging my phone.
I have a 2 different "travel pouches" so I don't have to build it up for every trip, I just remember to pack them. In my electronics pouch, I keep my multi-plug USB outlet, extra charging cords and plugs. In my "everything else" pouch I keep a roll of packing tape, small scissors, medium and fine tip sharpie, post it notes, ear plugs night light, sm flash light, clothespins or chip clips (I also keep a set of magnetic clips so I can put a note on the fridge), laundry pods/dryer sheets (in a recycled vitamin container), and kids' wrist bands that I custom ordered with my phone # on it.
You do so much walking at WDW. When we went for a 10 day trip, I cut out 2 layers of Dr Scholl's foam insoles for all of our shoes and it was a life saver. At this point, we have orthotic insoles, so I don't have to sit on the floor cutting out the foam feet shapes anymore, lol.