Very controversial... MANY respectable people say "cold pitching" (meaning not warming the yeast before pitching) leads to less lag time and more complete fermentations. Denny Conn is one of them and a quite a few microbiologists agree. Yeast are harmed by the "freeze" part of the freeze-thaw cycle, not the "thaw." Note: instead of flaming, please ask for citations and I'll post them. I don't want to flood the thread for something off topic.
Yes you can wait the week, but you can always just over-pitch which, within a reasonable quantity, won't hurt anything and probably only help.
UNDER-pitching, however, can lead to off-flavors and stuck fermentations. You'll wear out the yeast prematurely and you'll need a lot more aeration. (which, btw, for best yeast performance, one should aerate twice; once before pitching and again 12 hours after.)
Also, learn to wash or bank yeast man! You'll save hundreds.
Good luck man!