Havent read any of your replies but this is what we did for DDs 1st birthday and it was a great day.
We had it in our garden, lucky enough to have a big garden so no problem there and it was in august so nice weather (qld) and didnt rain.
For the invites i Took a nice photo of DD and at the photo shop i added some text just saying DD is 1 etc and printed them off and posted photo invites, worked out at about 20c each plus postage!!!!
Cakes, i made a few batches of cup cakes in the weeks running up to the party and froze them, got them out the freezer the morning of the party, whipped up a quick butter frostong and pipped it on, a few sprinkles and it looked like id bought them!!
As for food, just did a bit of a bbq, mini sausages in those mini dinner rolls and mini risoles. quiche, salads etc, really easy. A tote box full of ice and a few bottles of wine/beer and we had a great day!!
Even though i was adament that the day was all about DD, when it came to it, she just had fun looking at all the people in her garden so it didnt make to much difference what we did, It was a great day for me and DP! Have fun!