Not just great gifts for kids....I am 32 and still ask for them for birthdays and christmas!
DDollars really are just like a gift card, except in cash increments, and as described above, like monopoly money. You can get cash back from purchases when you use DDollars, so that is different from a gift card. I believe you can purchase them at world of Disney and maybe city hall??? Usually, we get them at Disney Stores prior to leaving.