B.W.
I dont think you need any kind of theme party for a one year old. For my daughter's first birthday, i just made a dirt cake, got some cute birthday plates and hung balloons. I ordered food from walmart. They do fried chicken and rolls and potato salad or baked beans for really cheap. I got a little favor bags for the kids just filled with a little bit of candy and a toy from the dollar store. I didn't organize any games or anything, we just mingled like you said. I thought it went well. good luck!