I've only been carded once at Disney.
Usually, I'm w/ DH, & I guess it's obvious that we're over 21 when we're together maybe, especially when the kids are w/ us. I don't know...
Anyway, last time, DH & the kids were doing one of the Phineas & Ferb adventure-things, so I walked on ahead & stopped at the "Joy of Tea" stand in China. I ordered a Green Tea Plum Slush, & the castmember asked me for my ID.
And, of course, I didn't have it w/ me, because I never carry my ID w/ me at WDW. So, I said, "Uh.. I don't have it w/ me, but I can run back & get my husband who has his w/ him..."
He said something like "It's okay" & went ahead & let me have my drink.