Here are a few little hints that might help convention go-ers.
Lugging so much back and forth is tiresome. I swear by the end of convention my arms are longer. Pack only what you need daily in the showroom. Pack grain in quart size ziplock baggies, write the day of the week on them. Don't lug pounds and pounds of grain back and forth. Keep the bulk of it in your vehicle.
There are several brands of grain provided free by distributors at convention but make sure YOUR brand will be available. Stressful convention week isn't the time to switch feeds. Give a bag of your brand with each rabbit you sell.
It is amazing how much hay you can get into empty bread bags. Just keep packing it in. When it is full, put a tie on it and SIT on it. You read that right - SIT on it! This compacts it even more. These "flat flakes" fit nicely under car seats. If putting carriers into kennels, put a rug on the top cage and lay some of these hay bags on top. They certainly won't add any weight to the kennel.
If you can drive it in a day, consider not packing your own water if vehicle space is at a premium. Stop just before getting to the showroom and pick up a couple of gallons. Write you name on them so they don't disappear on you.
I've heard of some folks putting carriers on top of egg crate foam to provide a smoother ride for their convention bound rabbits. This might be especially helpful when transported by pickup trucks or other less smooth riding vehicles.