Does he have a particular theme in mind for his party? That could make it easier to think of things to do. If it's nice out and you have some room, maybe you could have lawn bowling or horseshoes outdoors. Maybe you could set up a scavenger hunt -put the boys in groups and give them each a list of things to find in the backyard or the neighborhood (I'd have adults or teenagers accompany them outside though.) Send them with polaroid cameras to record their finds.
Indoors you could set up a treasure hunt with clues to follow and prizes to find. An archaelogical dig might be fun - you can make small plaster of paris pieces with a toy inside ahead of time and have the kids chip away the plaster to find the toy. (I think if you mix some sand in the plaster it makes it more crumbly and easier to break.) If someone has a karaoke machine and tapes they might enjoy putting on their own version of American Idol.
If you're adventurous, you could direct them in making their own dinner
Boys are very good cooks and don't always get the chance to play in the kitchen. With such a large crowd I'd separate them - just like a real restaurant kitchen staff- and have a salad group, pizza group and dessert group. Some could even be put on breakfast duty the next morning. They might like to try out recipes from Top Secret Recipes, where you try to recreate popular foods at home. Then you could have a taste test to see how their creations stack up.
Board games such as Pictionary, Scattergories, Cranium or Trivial Pursuit can be played with large groups. Pictionary can be really fun if you set up a large easel with paper, like they used to do on the old game show.
Since it's fall soon, bobbing for apples or the donut on a string contest are fun activities. (The donut game is you string donuts along a horizontal line in front of the kids, adjusting the donut height to their height. Then without using their hands the kids have to see who can eat all of their donut first. It's harder than it sounds!)
Family Fun has great ideas (
www.familyfun.com) - they have a sleepover cake that you could adapt to be more masculine, or I think they have a camp-out cake you could use - and lots of game & craft ideas. And teach them the wintergreen Lifesavors trick - they'll love that! (In a really dark room, if you crunch down with your molars on a wintergreen Lifesavor - leaving your mouth partially open - you'll see green sparks.) Have fun!
