As you are in Kent I think you could do this in one if you have an early ferry. We usually cross 11 ish and stop at Le Mans on our way further down - so Somewhere around Tours would definitely be doable in the day without rushing.
we stayed at Parc de Fierbois near Tours 3 years ago, with our friends and their kids, aging from 6 - 12. They all enjoyed this site and enternainment went on in the evenings. We didnt tow and found it quite a journey in one day but if you caught an early ferry it is doable, I think its about 340 miles but not sure. The pool complex was nice and table tennis etc. Following year stayed in a static at Parc des Alicourts, really nice site but we went in May, weather was poor. Pool complex was fantastic and had a lovely new indoor pool/spa (trunks only) which was lovely especially as so much rain. It has a lake which you can swim in and a nice bar overlooking the pool. There was a golf course right next door. The only drawback is need to drive everywhere. Hope this is of help.
Have a look at the Eurocamp brochure, or website www.eurocamp.co.uk. They have 'categories' of sites which are suitable for certain groups - and teenagers is one of the groupings they use. The Eurocamp 'teenage' club is called 'Base' and it appears that the only site in the Loire offering this is Le Parc de Fierbois, at St Catherine. However, this is likely to mean that there will be lots of other teenagers on site, and plenty of activities to keep them from 'boredom'.
Another site, but not in the Loire, which is good for teens is La Croix du Vieux Pont and Berny Riviere, near to Soissons. It has a good range of activities, something going on every day, and has been recommended by families with teenagers. It also runs a coach trip to Disney (extra payment, obviously). It has a very big British presence, so may not be too daunting for a first time in France.
Having said all that, many French campsites have a lot going on for children of every age, and others with teenagers may be able to give you more guidance. (Mine were teenagers once - and came with us - but it's a while ago now).
Don't forget to leave a review of the French and other European campsites you have visited!
The Loire is a big area, but Calais to La Loire is about 300 + miles. If you go via autoroutes you will average around 50 mph, so 6 hrs without stops, expensive in tollls. Via routes national your average will be nearer 40 mph, so you may decide to have an overnight stop.
There have been many discussions on here whether to go via Paris or Rouen, and I think the balance of opinion is in favour of Rouen, There are also links to a number of stopover sites around Rouen, but here is one for example http://www.ukcampsite.co.uk/sites/details.asp?revid=6601
Re which site you choose, I suggest you type Loire into Search above. This should keep you going until it is time to go on holiday.
Since we always cross into Cherbourg or Le Havre, we don't ever use Calais, so I don't really know that road. However, I have always found if it's a close thing between using an overnight and not, then do use one, because then you're not stressing about boats running late or getting held up for an hour in traffic. There's a nice municipal at Vimoutiers, just off the A28, a few miles North of Alencon.
We have stayed at about 12 different sites in the Loire region, leaving Calais around 07.30 Have always reached the sites between 2 & 3pm. I'd agree that Le Parc de Fierbois would be an ideal first site for a teenager.
------------- Ally
Don't forget to leave a review of the French and other European campsites you have visited!
I agree Parc De Fierbois is an excellent children's site lots to do on site! Visit the zoo near there if you get chance it's amazing (I can't remember the name of it) and so big we didn't get around all of it in one day)
my only concern is the camping pitches (I've never Caravanned there have stayed there in mobile) but we did investigate the camping pitches as we are caravanners and the ones that were shaded were quite muddy but the weather hadn't been great before we arrive. I don't know whether anyone else would be able to comment better on the pitches, it might just be because the weather wasn't great at the time.!
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.