This is fun: Umbrella - 1. dome of the sky; 2. verticalisation: the cosmic tree, the phallic father; 3.a sun-emblem; cf. parasol and sunshade; 4. divine and royal power, protection; 5. mourning; 6 folklore; it is unlucky to open one when not needed. De Vries, Arthur. Elsevier's Dictionary of Symbols and Imagery. 2nd. ed. Bingley: Emerald Publishing, 2009. Print.
A couple thoughts: In the dream the umbrella is put to good use even though it's not used for what it's intended for - protection from rain. Umbrellas are synonymous with floating or flying (to most of us) even if we haven't seen Mary Poppins. The more I look at this dream, the more I feel like the umbrellas are trying to tell me something. Like they have an anima that has a goal of leading me toward something.