Will try to cover this as best as I can!
Find a spa place that will donate a portable hot tub. Place it on your lawn in front of house!
Contact the local media, paper and TV to let them know when the event is along with the Charity and Soroity you are sponsering. Make sure they will post something before hand and will be there during the event!
Have a big board near the tub so you can list all of the people who donated what and as they come by and donate $ or canned food put the name on the board for all driving by and or stopping. A sheet of plywood and paper.
Pick a worthwhile Charity so people will know it is worthwhile!
You can get a lot of great PR and meet some ladys and it does not cost much!
If someone else does it throw a little different twist on it. Do when cool as the steam rising looks great.
So far, after talking with Brother Jacob Lee, U R I he was the second and had a great time and it looks like we now have 4 Zetas involved!
Good Luck and keep us all updated!