i agree, most everywhere i go i use my 17-55mm. the 70-200mm is only used when i need extreme closeups, for example i used it recently at two graduations.
unless youre gonna be doing nature shots of animals while youre on vacation, i think youll be using the 18-55mm more often. if youre going to the zoo on vacation, then the 55-200 will come in handy
if youll be taking shots of the family on vacation, the speedlight will be extremely valuable. almost every shot i take of people uses my speedlight.
and a note on the super wide-to zoom lenses. i had the 18-200mm VR and i didnt like it. its a great versatile all-in-one lens, but the image quality suffers from any lens that offers such a wide zoom range. youll get much much better image quality from an 18-55/55-200mm combo.
there's a reason serious photographers dont even use zoom lenses and stick only with prime lenses (50mm, 85mm, 105mm, 300mm, 600mm, etc etc)