
I would thoroughly recommend having something to make a garden with - I use the barrier netting that is used on building sites - as it means the dogs can wander around the garden when you are there with them and makes for a far more enjoyable experience. Remember to take covers for your car as well if you are leaving them in there whilst walking the course etc - caravans can get very warm and open windows can be a problem if you have to leave the dogs there alone at all.
A towel for wiping wet dogs down is a must and also wellies for you as first thing in the morning the ground can be very wet with dew. A large bucket of water outside your unit doubles as a drinking station for the dogs and for fire safety - usually the regulations iro camping stipulate that you must have either a bucket of water or a fire extinguisher situated outside your unit.
I have just started camping at agility shows in a tent and have camped twice so far (other 2 shows were cancelled due to the weather) and have another camping show booked for later on in the month and it is sooooooooooo nice not to have to face a long drive home after a day competing only to drive all the way back again the next morning.
I am sure you'll have a great time and good luck with your runs :-)