Don't underestimate the polystyrene cooler boxes found in Walmart and Publix etc. for about $4. We bought one when we were going to Merritt Island to watch a shuttle launch, knowing they advised to get there about 3 hours prior to launch and packed it not knowing whether the salad etc. would be in any condition to eat as it was mid August and in the 90's. As well as a couple of the ice blocks, we froze a few Capri sun drinks to act as ice blocks (good tip for the kids actually if you freeze these - they can either have them as lollies or wait until they start to melt a bit and they are a bit like slush puppies), we even put chocolate in to see how it fared. Six hours later everything was still cold and some of the drinks hadn't even started to thaw. We left it for guests to use and it's still there 6 months later.

steph