Halloween is my favorite holiday! I have a million ideas.
What kind of costume do you want for her? Mainstream (pumpkin, ghost, some store bought character.) or make your own (pirate, doctor, prisoner) or something completely original (static cling, ceiling fan, time flies etc.)
Last year I was a blind surgeon. I wore my scrubs and splashed them with fake blood. I also wore sunglasses and a name tag that read "Dr. B. Lind, Dept of Surgery" My stethoscope was backwards and I also had a few surgical instruments (just kelly clamps and hemostats) in my pockets and attached to my shirt.
For treats...cookies in the shape of halloween things (Pillsbury even sells them!) Or cauldron cupcakes (bake chocolate cupcakes with a marshmallow in the middle of them. There will be a hole in the middle. Attach a licorice "handle".
bake a sheet cake, cut into a ghost (or pumpkin or witch's hat) and decorate.
I tilted all the pictures in my house and put fake spider web stuff on them. I also made a scarecrow, put him on the hearth. This year I'm working on a way to get him to talk...I want to use a Sim-man from the hospital, but the the owner would never ok that...
I had a skeleton greet people at the door. My flowerbox became a graveyard with funny sayings.
Oh, I never started my sarcophagus! I'm making one for my aunt's living room. Different stores will have toys that light up and sing. I have a skeleton's head that sings "hot hot hot" and it looks like fire is coming out of his head. I also have a witch's hat that sings a halloween version of "do you believe in magic"
ohh, my aunt also made me a purse that looks like frankensten and it says things like "its my first halloween...boo! did i scare you?" and "if i'm real good, can we go halloween caroling...please?" You can find things like that at Party City and make it into something she can hold her candy in.
Also, most malls sometimes offer trick-or-treating.
There's so much to do! I can't wait to decorate! I should do that this weekend.