We have taken the car from Northern Ireland to France many times .. so it will probably be a longer journey than yours. We have met many from all over Ireland and Scotland who have drove too. We find that as long as we take a break/stop every 2.5 to 3 hours the ling journeys can be very "bearable" for the children.
If you are bamboozled with all the options, then i suggest narrowing it down.
Firstly narrow down where you want to go. I suggest Vendee area for a first time. Far enough south to get good weather but only 4 to 6 hours from uk ferry crossings.
Secondly decide if you want to drive or fly. Get approx prices for airport (parking, flights, luggage, carhire). How close to airport are you, and how close is the airport at the other side?
Then compare with driving. How far are you from south coast? I allow 15p per mile as a rough cost. Also french toll roads (guess £25 but depends on where you travelling to / from). Would you be willing to drive the distance? Also bear in mind you may be able to bring extras (e.g. toys, bicycles etc).
Then narrow down and read up on revievs for your potential suppliers. Canvas are good for kids clubs but expensive. French Freedom, Eurocamp, Venue (our favourite). This will give you specific costs and location for sites (bear in mind some of these will include ferry crossings already).
You will collect a lot of information in a couple of nights researching, but you need to do the leg work as you know what you and your family will accept.
Don't worry about getting it 100% first year ... as it is an adventure, and you will learn a lit the first year, and tweak what you want to do in future years. We have been doing various options of this holiday with different travel plans and locations for 13 years now!! Brilliant holiday, and always an adventure!!!
When you have done some work, why not come back and ask more direct questions on specific suggestions/recommendations. Also the companies (Canvas, Eurocamps Venue etc) are excellent at taking you through the options and giving you prices.