Most definitely get hold of a portacot if you don't have one or a playpen, especially if camping anywhere near water!! That way if everyone is busy setting up camp, cooking etc you can keep the littler ones in one place where they are safe and can't get into anything they shouldn't be.
The best thing that we invested in was a Tent Cot
...it's fantastic for keeping the mozzies etc out but you can roll the sides up when it's hot so the bubs stay cool, plus they can't roll out of it. Not to mention being able to move it outside into the shade or breeze.
Another thing is make sure you take some toys eg bikes for the older ones, colouring books for quiet times and a portable dvd player can come in handy too if (heaven forbid) it rains LOL....there is nothing
worse than being cooped up in a tent when the weather sucks with bored kids!!
Clothes airers are good cos they fold down for easy storage, or use pegs on rope to hang towels. Do NOT forget a can opener!!!