For a cake - I didn't want all the sugar that is in "normal" cakes, so I made a pumpkin apple cake with cream cheese frosting. It was delicious, and much healthier than most cakes. Even my please-feed-me-chocolate friends liked it.
My kids FAVORITE things at their first b-day parties were the balloons. We bought a big bag of balloons and blew them up and made a balloon pit in the living room. The little ones went nuts over it. Another thing that we did was to ask for "consumable" gifts, like gift certificates. Rather than getting a bunch of toys that we didn't have room for and that would be broken in a few months, we were able to get a yearlong pass to the Denver Zoo, and a yearlong pass to a local petting zoo. If your daughter has a favorite place to play, like Pump It Up, those also make fun gift certificates.
At this age, keep the party simple, and keep it fairly short. Make sure that it is after your little one's nap. When she gets burned out with all the excitement and guests (and she probably will!), have somewhere quiet that she can retreat with you or Daddy. Also, I designated someone to take pictures, which was a huge help when I was coordinating things or when I wanted to be in some of the pictures.
Best of luck, and Happy Birthday!
Cheers,
S.