The one piece of advice I'd give anyone is bin the sleeping bags and take decent duvets instead, much better. If you've got space for it some sort of toilet is handy for night time, doesn't have to be expensive, a bucket with a lid will do the job!
Here's what I consider to be "essential" and what I take for two days in the hills; I know people who would consider this list to be excessive! O.k. for car camping I fill a Honda CR-V but tent carpets, DVD players and flat screen tellies etc. are not essentials, they're extras!
Rucksack
Tent
Tent rag
Bivi bag
Sleeping bag
Sleeping bag liner
Sleeping mat
Teddy bear
Head torch
Poo shovel
Bog paper
Stove
Gas for stove
Pot
Lid for pot
Pot handle
Matches
Tea spoon
Desert spoon
Knife
Mug
Water bottle
Collapsable water bottle
Washing up sponge
Packed lunch day 1
Packed lunch day 2
Coffee
Powdered milk
"Wayfarer" dinner: 2 days.
"Wayfarer" pudding: 2 days
Fruit
Muesli bars
Porridge
Waterproof coat
Big fleece
Waterproof trousers
Gloves
Hat
Spare top
Spare pants
Spare socks
Towel
Antiseptic hand cleaner
Deodorant
Tooth brush
Tooth paste
Nivea cream
First aid kit
Map case
Map
Telephone
Pacing beads
Watch
Whistle
Paper
Pencils
Compass
We don't always take our table and stools (tiny wee light things anyway!) as some sites supply picnic tables or we find a nice comfy rock or tree stump to sit on. A good tent, warm bedding, something to cook on/with and a torch - that's all you really need.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.