They MAY be, but they may also tell anyone who asks to take a flying leap off Paradise Pier or into the Rivers of America.
What?
I go to Disneyland like every week. And I get asked for an ID almost every time I make a purchase. Legally, every merchant is supposed to check your ID with every purchase. Most don't but Disneyland is pretty strict about it. If you don't show it, they will simply deny your purchase.