How much time should I allow before flight at CDG

3 hrs should be fine, are you taking a taxi, metro or shuttle? The reason I ask a taxi is fast & reliable, the metro is cheap & reliable but some are faster than others so check, a shuttle is a two edged sword because sometimes they pickup from multiple hotels and your 3 hr head start can be shaved to two hrs.

CDG is very modern and well marked, just make sure you know which terminal you want to go to. I like traveling through CDG because I just take a carry on backpack and once I arrive you can jump on the metro at the airport and be in Paris center very quickly.

the metro doesn't go to the airport and once you board an RER train to the airport no 'faster train' is going to pass you. If you use the metro to get to an RER B station, you will also be hauling luggage up and down stairs on the transfer to the RER system. The train is usually the quickest guarantee BUT there have been reports of shut downs due to security alerts and the occasional strike, so it is always useful to have a plan B. We usually take a taxi now and give it an hour; it usually takes a bit less than that but if it is in peak rush hour give a little more time. I would never take a shuttle TO the airport when a slow ride means a missed flight. We once many many years ago were on a shuttle that got lost trying to find its last pick up and got us there 45 minutes later than it should have. We barely made the plan; today with heightened security we would have missed the plane.

I was there yesterday and it was fine. There is a strike that starts today until 2 August, but it may or may not impact your flight depending on the carrier.

http://www.airfrance.us/US/en/common/page_flottante/hp/news_air_traffic_air_france.htm

90% of long haul flights are going during the strike. The strike is only Air France.
However, this Saturday is the heaviest travel day of the year in France--French August vacationers leaving and July vacationers returning. Be sure you allow the full three hours.

The current strike ONLY AFFECTS AIR FRANCE flights. It is only AirFrance personnel striking.

Thank you for the responses! Most helpful! We plan to take a taxi. Figured that would be easier. My departure is Sept. 3rd. I like to travel at the end of August.

There is a new flat fee for taxis going to and from both airports.
Depending on your address, you'll pay 50 or 55 EU for 4 passengers and their luggage.
Go to the official taxi queue in the airport, and hand the driver the complete printed address of where you're staying - include the Postal Code.
If you need to pay by credit card (no AX accepted), ask before getting into the taxi.
No need to tip, unless the driver helps with the luggage - up to 5 EU is plenty.

Thanks for the info on the flat fee to the airport.