Hi Laura,
I did this for my boyfriend's 5oth birthday. It two years of planning and involved a P.O. box for the inivations to be mailed from and RSVPs returned to. I sent out 200 and 2/3 showed up for the party. I Supplied the hamburgers and hotdogs and asked everyone else to bring something from a list of appropriate foods. I encouraged them to make it easy and didn't mind if it wasn't home made-- grocery store deli counter was fine. They got their food buffet style and drinks were bottles and cans of juices and sodas and a pony keg of good beer. I did have a friend or two that loves to grill and they were asked ahead of time to be incharge to the grill. I also asked key people to help with the restocking of food and plates and had a clean up committee all arranged prior to the party. I rented a room at a Municiple park building and we walked into an empty room and four hours walked out of the room in the same condition as we found it. EVERYONE pitched in and helped.
I also did cooking right infront of him, asked him to taste test by using the exuse that somebody eles was catering a party and need some help. Maybe a coworker/friend has a niece that has a wedding?

I also know a woman whose husband had been a welder. I used his helmet when I walked the light cake to the Birhtday Boy. I used a device to light the candles so that I didn't have to hassle with matches. Try looking in the B-B-Q section for an "Aim-n-Flame". I think by BIC and well worth the few dollars I paid. I used a single layer cake and cut the ice cream into squares just like I cut up the cake. I rented a wheelchair from a medical supply service and decorated it as the chair of honor.
I set out disposable cameras and the kids had a blast taking pictures of everyone. Perhaps a few too many from behind.... but thats kids. I also had about 5 people tell a short story that was typical of the guest of honor. Not realy a roast just funny stories.
The only thing that I could not have imagined, planned for or gotten through was the torrential down pour. everyone was a good sport at having an indoor picnic.
I hope that this helps make the party enjoyable for you as well.

Julie