Hi Emmagee,
The family camping has its own site entrance and car park, and is an enormous sloping field. So you can camp pretty close to your car if you want, however that means that each time you go into the festival you have to walk that much further, so I'd say it might be better to camp nearer the festival end of the field, although those initial journeys will be longer - and even then the distance to your vehicle really isn't huge if you compare it to a glastonbury or something.
We were in the family / live in vehicle enclosure last year which is at the bottom of the family camping field, and actually it was quite cramped - maybe it's getting more and more popular to take a camper? Also there was no organisation to it, so had we wanted to leave early, it would have been totally impossible due to vehicles all around. The shrewd people had just driven their campers into the main family camping field, where there was much more space.
Hmm will miss it this year! Have fun!