Yeah, yeah... sure you are free... you are always SUCH a tease!!

Let me help you prune down your options.

I've found rollable solar panals that are rad if your camped somewhere. My laptop takes ~65W to run just that I would need 5 of these units totaling a 5' x 5' area. I think solar is just plane unfeasable for 5kW even if you could get much higher efficiency solar panels.

Fuel cells although new and intersting are very expensive and oddly make allot of waist heat that must be dealt with. Sometime on the horizon we will see small units for cell phones and laptops, but they will be very expensive.

That leavs you two major options:

gas generators and batteries

Since the batteries need to be charged taking an enormous battery bank into the woods is pretty much unfeasable. The ham radio folks do it but their not using quite as much power as you need to throw a party.

This leavs generators. I know that diesel in general is the most efficient way to generate power and that most diesel generators can be converted to biodesel if you like.

I think you major concern is polution? Being green house gases and noise. Like cars you can add a muffler to the generator. Most people don't realize that the sound comes out of the end of your tailpipe mostly. You could solve two problems at once. Add a catalytic converter and muffler to your 6kW generator and connect a hose to the end of the muffler and take the exhaust and noise away from the party. Be sure to get a thermaly rated hose. I have seen them in professional auto shops and race tracks.