Hi Gill
You have made a good choice with the lakeside pitch any that i seen had some shade. We used the Dover /Dunkirk route we then used the A1 for Paris, it onlycost euro 21 for that journey. We then followed the A86 around Paris and joined the A10-A71-E9 signed Orleans-Chateauroux-Bourge.The journey took us just over 6 hours. The toll for the second part of the journey was 19euro.
From the site it would be a long way for you to travel to Eurodisney it would be better if you stayed at maybe a site nearer to Paris. A good choice would be www.la-croix-du-vieux-pont.com They even have a bus which does day trips to eurodisney and Par Asterix.
If you need any other directions to the site let me know. By the way that site i mentioned is only 3 hours from Calais and is not to far off the road . it could be used to break up your journey.