Charles De Gaulle, Paris

How about a cafe in the terminal? The airport has free WiFi to kill time with.
http://easycdg.com/passenger-information/arrivals-cdg-airport/

I'd also make sure you have a Plan B in case one of the flights is delayed. All should have the address of your lodging, local currency or the ability to get some and a time frame to wait before heading in to town on your own.

There is a Sheraton Hotel at Terminal 2. Their lobby would be a good place to meet. There is also nearby Paul's bakery where they could get something to eat and drink while they wait.

I would not wait around an airport or hotel lobby for 'hours' for a friend arriving later unless that friend were disabled or it were my daughter with her small children etc. The first people there within an hour or two of each other should head for the hotel or apartment and the latecomer should meet them there IMHO. If you have an apartment the early arrivers can get things set up, go buy basic supplies etc. If hotel, they can stow luggage and check out the neighborhood.

A café or hotel lobby will be about the only place to sit down. Airport arrivals halls in general are not designed for lounging. Janet has offered you a better plan.

I can see some logic to waiting 2 hours if you'll all share a flat-rate (50 or 55 euro) taxi into the city. Tasks you could handle in the airport include getting cash from an ATM, buying Metro tickets or passes for the group to use later, and buying Paris Museum Passes at the Paris Tourism desk.

LOL. I read is JULY Second hours after. rather than July -- 2 hours after. So yeah maybe wait, but have a plan B if there is a delay.