Hi, DB,
I see I am against the stream here, but the best parties I did for my boys were pirate and Native American themes. We had a storyteller for the Native party who kept some 20 6-yr-olds and younger entranced for an hour; found him through the American Indian Center, I think. Before stories, we painted faces and the kids made feather headdresses (materials from Constructive Playthings) and then ran around outdoors after storyteller and cake. For the pirate party (which I have done at least 3 times and this was before Pirates of the Caribbean), they walked the plank to come in and immediately got scoundrel face paint, bandanna and a pirate name w/tag. Then we played pin the eyepatch on the scoundrel, did a treasure hunt in the yard (loot from CP), trading of loot if they want to, then cake.
I know you are thinking, yikes! not in the house!!!!! But you can do these at a community center or other location from those below that will allow you to bring in your own stuff. Worth a try to do something different and more personal, if your little guy is into pirates or Native American culture -- his birthday is certainly at the right time of the year -- and my kids still remember these parties happily. I will not suggest the ancient Egyptians party as that was a little esoteric!
Enjoy,
Mama S.