We're fairly new to camping too, but I think the trick is to know what facilities your chosen camp site offers. It sounds obvious but we took so much stuff the first time that we didn't need eg. washing up bowl when there were set up facilities with running water and bowls, big water storage bottles when there was plenty nearby on tap etc. So if you can figure that out, you can leave lots at home.
Do bring:
- easy food to serve to the kids when you arrive and haven't set up yet
- crocs for kids to throw on easily whatever the time of day or night
- anti bac wet wipes are so useful!
- a proper ice box (not ice bag) with plenty of capacity for all your food and drinks
- good, safe (dimmable) lighting that can hang inside your tent for when the kids go to sleep
- more marshmallows and wine that you think!!
You'll have great fun and the kids will love the freedom. And ignore your friend, your tent will be just fine!
As to location, so far we have tried these two and both are brilliant.
http://www.seabarnfarm.co.uk/
http://www.wowo.co.uk/
You'll have a brilliant time, PM me if you have questions - happy to assist