I can totally sympathize with you on this one. My youngest will be 1 on 11/26 which also just happens to be thanksgiving this year! Everybody will already be at the house so we are just going to do a "smash the cake party."
Any who, It sounds like you have put a lot of thought into your daughter's 1st birthday and have a really cute theme to go along with it. I say why not? She is little and you only get to pick what the the theme is for so long before they start voicing their own opinions.
And there is SO much you can do with this theme. If you are worried it might look like a Halloween party instead for her b-day then mix together decor and party favors. Like pink and black balloons & plates etc. Throwing in Pumpkins where you can since orange will go with those colors as well. That could be really cute! Have a special cake made to match along with your favor bags.
Last year I had a Halloween themed baby shower and we had a pumpkin piñata, pin the nose on the jack o' lantern, mini pumpkin decorating contest and other games. We made it kind of like a carnival. All the kids, even the teens, had a great time. I think we will do it again this year just for fun!