What should I eat the day before a weigh in to healthily lose weight?

I am a rower and am just about even with the lightweight cutoff. What should I eat on the long bus-rides to our Regattas and what should I eat the breakfast and lunch the day before? The basic Idea I have is this, Cereal for breakfast (nothing abnormal), and a light salad for lunch (is low-fat dressing ok or is that too much sodium?). On the bus-ride over I was thinking I should bring fiberfull cereal so that everything gets cleaned out when I arrive at the hotel. Should this work to make sure I don't gain any weight?