Our group has a 12 hr layover in Paris. We'll be arriving at 11:30am. Are there any tours available that will pick us up and return us to CDG airport?
You may want to consider taking the Air France shuttle outside of gate 2A to the Arc and Champs stop. It's a 25 min ride. Walk down the Champs eat a wonderful lunch and then take the Batobus which is a hop on hop off boat shuttle on the Seine. It stops at eight seightseing destinations. Look for specifics on their web site.
I had the same thing several years ago and took a Roissy bus from the airport into town. I had bought a "streetwise Paris" map at B&Noble to take with me. It also had a map of the subways. I don't remember the name of the tour company, but there were groups of them across the street from the Louvre (pyramid thing si behind you, go diagonally across the street to the left and about 500 ft forward, you'll see signs everywhere)
I started my layover with a 2hr bus tour, in an air conditioned double decker bus with English available on the headset. I think it was around 25 euro. I camped out upstairs with all my carry-on junk and snoozed most of the way through it. It was summer and I was hot, tired, and as a solo traveler needed a safe place to crash with my stuff. ;) It was worth it. After the tour I bashed around town via the subway and saw what I'd put on my short list of must-sees.
Based on my experience in touring Paris, the two suggestions listed here seem to be what I would do.
I doubt there is a tour which will take you from CDG. Go into the city center for the most choices available.
I always go to the Tourist Information Office in each town to ask about bus tours and take the clerks advice on which to take, based on my time limits.
Be sure to allow more time than you need to return to the air terminal to handle unexpected delays.