Charles De Gaulle airport to Versailles

Hi,
With 6 people a taxi (you need a van, but easy to get that at the airport) is indeed better but... What will you do with your luggage? There are some private luggage storage operations in Versailles but it's inconvenient. Also, Versailles is a fairly strenuous visit due to the amount of walking involved: not great after a long flight.
You get my drill : maybe keep Versailles for another day?
As for getting around: you can rent bikes to get around the grounds, but for the gardens close to the Château, the only way is to walk.

Even if you were all eager to see Versailles, it's not how I'd want to spend my first day, particularly in your situation. Here's why:

1) You said your kids don't really want to go. This will make a very bad start to the trip, possibly not only resulting in a bad first day, but bad attitudes for whole trip. Teenagers are difficult enough - why create more problems from the get-go by taking them to a place they don't want to see? If you wait until later in the trip, you can make sure you've first gone to some of their own must-sees, then take them to yours.
2) Travel and time zone changes hit everyone differently, but for many (often including me), the first day of arrival is a jet lagged haze. It's bound to be that way for at least some of your party.
3) By all reports, Versailles is now mobbed all day, every day it's open. Even for rested and eager visitors, that's no fun. But it goes double if you're sleepy and foggy.
4) It's also large, so it takes stamina to see.
5) It's not cheap, so if you aren't having a good time or are exhausted and decide to leave early, you'll "throw away" a lot of money.

For arrival day, a much better plan is to drop your bags at your hotel, then just walk around Paris, possibly following Rick's Heart of Paris walk as a rough guide. Or, you could just walk around your hotel's neighborhood, observing all the little "French things" you will see, which the kids should find interesting (assuming they have not been to Paris before). Or, go to the Trocadero and take in the great view of the Eiffel Tower for that "I'm really in Paris!" moment that both kids and adults will love. If people are feeling energetic, you can go the Arc de Triomphe and climb to the top for great views, as well as lots of entertainment watching the traffic below.

I wouldn't plan time indoors at anything, and wouldn't plan anything involving pre-payment or strict times.

My €0.02.

I'd restart the vacation planning. My first step would be to require each of the 4 kids to plan at least a half day of the trip. give them guide books and a time slot. Nothing makes a family trip more miserable than dragging kids to things they don't want to do. When they have to. plan for other people's pleasure they tend to be more cooperative at doing things you want to do.

We have seen so many things we would not have seen because of our kids. Our son took us to the John Soanes Museum in London, the Aquaduct Park in Rome, the Specalo and Galileo Museums in Florence; our daughter took us up the Tower at Notre Dame, to the Cluny in Paris and the British Library in London (who knew that would be so interesting?). She also took us to the zoo which I thought was a drag but she loved it.

Second with 6 people plan to split up in teams from time to time and meet up to share adventures. worked when we were just 4 or 5 -- even more important with 6.

And finally Versailles is a painful experience when you love it -- it is going to be a very sour way to start a trip with a family of tired teens who don't want to be there. Don't go without timed tickets so they aren't standing in the sun for two hours to get in; don't go when people are tired; consider not going at all unless it is at the top of your personal list in which case the kids can go along in exchange for you going along with their plans.