Here's a little info I obtain elsewhere:
Disney Dollars are "cash equivalents." One Disney Dollar = one US dollar. They can be used at Disney Store locations in the US and at almost all locations in Walt Disney World Resort, Disneyland Resort and Disney Cruise Line. Disney Dollars can be purchased at any Disney Store or Disney theme park, or by letter from Walt Disney World Ticketing, PO Box 10140, Lake Buena Vista, FL 32830. You must pay in advance. Shipping is $10.00 for express delivery. Include shipping charges with the check.
Just got home and found some more info for you. You can order them through Walt Disney World Mail Order at 407/363-6200
Ask about who is on each bill. There is a varity of Disney charactors. Your son will have a blast and be tickled to death with your idea, make him take out the garbage or clean up though. You'll probably have the cleanest house around!