Hi, Hilary!
Playpen! (Travel cot does the same job of course, you'd probably have that anyway?) We had a Eurocamp hol when DS1 was not quite 2 and the cot/pen they provided was invaluable while cooking etc...of course if your 2-y-o is nearly 3 it probably doesn't apply. We went with our own tent when DS2 was just turned 1 and took our own travel cot.
Does the tent have a kitchen bay? We have a big 6 berth tent and ours doesn't, the place for the stove (under vented window) is just inside the tent door and it still bothers me even now kids are much older. With a bay it is tucked away. You need one of those proper camping stoves with 2 burners, pref with a grill too, and a folding "camp kitchen" to get it off the floor, with shelves for all the cooking kit.
You need a coolbox and some icepacks, most campsites will freeze them for you, otherwise milk etc is a problem, esp when it's warm. (If you can't get your icepacks frozen the coolbox makes a good ant-proof box for dry goods.)
Get a good camping table with height-adjustable legs. Also folding picnic chairs (sitting on the floor gets very wearing.) Also a camping gaz lantern. (Torches/battery lights inadequate.) Get airbeds from Argos, and they also have an excellent hand-pump, it's about 3' high but has double action, very efficient, and you can slot eg long sand spades into the box with it.
Take a small folding drying rack, even if you don't plan to do laundry it's useful for damp towels, pants etc.
Camping is great for kids, especially as they get older, you can let them roam quite safely, and it is a cheap hol - the only thing I hate is going to the loo in the middle of the night .
If I think of anything else I'll let you know!
Oh - what size car do you have? You'll probably need a roofbox or a trailer.
Hope I haven't put you off?