Also, if you take the key with you, it is unlikely that it will be taken. Not totally impossible, but in almost 8 years of being on the DIS Boards and other boards about travel to Disney, I have never heard of one being stolen.
Here is a list from the WDW website of attractions where guests in motorized vehicles,
ECVs, must transfer into an available wheelchair. At all the other attractions, you can choose to keep the
ECV in line with you or walk if the line and wait are short.
MK
Buzz Lightyear's Space Ranger Spin
"it's a small world"
Stitch's Great Escape!
The Magic Carpets of Aladdin
The Many Adventures of Winnie the Pooh
Tom Sawyer Island Rafts
Walt Disney World Railroad
Epcot
Universe of Energy: "Ellen's Energy Adventure"
Mexico: El Rio del Tiempo in Mexico (note: I just pulled this off the Disney site a few minutes ago, but it has not been updated to reflect the recent renovation to the Mexico ride. The boarding area has been renovated also and appeared to possibly be ECV accessible when we rode in April. Hopefully someone using an ECV can comment. At any rate, it's a short walk and the attraction is not that busy).
The Land: Living with the Land
Disney MGM Studio
The Great Movie Ride
The Magic of Disney Animation
AK
Affection section in Rafiki's Planet Watch
Kilimanjaro Safaris
TriceraTop Spin