I just threw MH a surprise bday party this past Friday and it sorta turned out like this on it's own.
I filled the house w/ balloons. (Walmart has a balloon and helium tank set for $20)
Streamers
Pin the tail on the donkey and I put pics of MH's face over top of the donkey's face.
Pinata filled w/ condoms, lube, and various things found at the Adult Mart
Jell-O shots
For food we had various dips, cheese platter, veggie platter. I threw meatballs and sauce in the crock pot and everyone made meatball sandwiches. That was the best thing I could have ever done!
I thought I would find most of the decorations at the party store but instead found so much of what I wanted at Walmart for dirt cheap. There's bday party packs w/ balloons, streamers, and two banners for just a dollar or two a piece.