Hi,
we have just booked with Keycamp for next July/August, after many, many hours deliberation over where to go. We chose keycamp because we wanted it to be as 'packagey' as possible as this is our first time, and Keycamp (although it is technically the same company)is cheaper tham Eurocamp.

There are 7 of us travelling doing a 3 centre holiday in Calais and Paris. We are having the bigest accommodation on each of the 3 sites we have chosen, and taking 2 cars. It is costing around £1900 in total, which i think is pretty good for a 2 week holiday.
Most of the sites in both the Eurocamp and Keycamp books have pools & slides as welll as many activities, which are essential to us as we are taking 3 kids aged 14, 9 and 5.
According to the brochures, the temp around calai will be pretty much the same as the south coast of England.... Paris should be a bit warmer, but the further away from Calais you go, the warmer it will be!

Good luck in choosing your holiday - I hope i've been a bit of help!

Helen