We won dream fast passes at DL 3 times. Twice it was on the exit walkway from Splash Mountain. Everyone who exited the ride received one, no matter their age, until they were all gone. Once it was at Ariel's Grotto before it opened. They were also given to everyone who walked in there (granted most adults only parties wouldn't go and see if Ariel was in or not).
It wouldn't be right if they only gave it to families with kids, but I dont think that's what they do. Actually, they're not great if you have little kids, since many of the FP rides have height requirements.