Horse show trip..?

Where will your horses be staying? WIll they have stalls? If you have one, a portable round pen is wonderful for long shows because there is typically no turn out and 10 days of no turnout can make a horse nuts. I would recommend an outdoor grill (the camping style one). A cooler is good and water bottles. Make sure you bring emergency kits for your horses with everything you might need if one gets hurt (including farrier tools if there is not going to be a farrier on site).