Assuming your child is very social and can handle a surprise, you can consider checking with a couple of his friends (who can be trusted not to blab) - my son is a little older and they like to hang out and watch DVDs a lot or listen to music. You might get someone to hook up their iPod to some speakers, or just bring CDs. My son's group went through a long phase of playing games like Uno and another board game - I think it's something about Apples & Oranges. You can ask a few kids to bring things they would like to do - you can always say you can't have too much stuff around because your kid will catch on and figure out the surprise. Other than that or having a ping pong table, the kids don't usually like organized games. Some kids like to do karaoke, but renting the equipment is an expense if they don't go for it.
Be sure that word of the party does not get out and you have a bunch of non-invited guests, particularly if there is a basement entrance that is not through the house. Have an extra set of parents on hand if necessary but do not let others into the party - this is the age when this type of problem starts. Having another 2 parents bring the food over - since you may be "hiding" it so your son doesn't catch on - is a great excuse to have them show up and hang around to help.
For food, the kids like snacks but also hearty foods like pasta and meatballs. I also make sweet & sour meatballs which they love - use the frozen turkey meatballs (available at BJs and some markets) and make a sauce of half chili sauce (like ketchup but a little spicier) and currant jelly. It's delicious. Keep it warm in a crock pot or one of those chafing dishes from BJs. The kids think this is SO cool. Put out a lot of cut vegies with baby carrots or sliced peppers & cukes, and a dip such as ranch dressing. If you put the microwave down there for the night, they can make their own popcorn. We put a small fridge in the basement for sodas, but you can use a big cooler full of ice and a few dozen cans of soda. They also devour those mini hot dogs (we get the all beef ones) wrapped in pastry - use the low fat crescent dough in the tube, but roll out the triangles and cut them into smaller ones - I usually get about 4 mini crescents per large crescent. Roll the little hot dog starting at the wide end of the triangle and ending with the point, and put them on a greased cookie sheet for about 20 minutes at 375 until browned. You can serve them on a plate with a small bowl of ketchup and a small one of mustard. Or you can do pizza, but have the pizza place cut the pies into 16s instead of 8s - makes it easier to pick up. Put out something to collect the cans for recycling, and a trash bucket, a stack of napkins, etc. Check in once in a while - under the guise of collecting cans and dirty plates, changing the garbage bag, or bringing down more food. Definitely be a presence but don't go down any more often than every 20 minutes. Put lots of paper hand towels in the bathroom that they will be using.
We always found that, by having our house be one of the prime hangouts, we always knew where our kid was and who his friends are! Have fun!