We never both messing with umbrellas but just throw on a poncho with the hood over it- its easier to navigate, and smaller to pack - plus those umbrellas can be weapons when squeezing through crowds, dragging them through stores, etc.
It rains almost everyday - come prepared with ponchos and umbrellas and you'll soon decide which is easiest for your family to mess wtih =)
(btw-dollar tree sells 2 pack ponchos for $1, that's cheap enough to throw away at the end of the day. They do sell the mickey ones in the parks, but be warned that you will be lost in a sea of them - its easier to hang onto your family/children if you wear a diff color or style)