MeVoy

I can't say if the RER is "safe" or not, but it does pass through some rather sketchy areas on its way into Paris. This might not be a cause for concern during the daytime, but at that time of night, you might find yourself somewhat uncomfortable as people get on and off at these stations on what is probably a 45-minute ride to Chatelet. You might want to check if the Air France coach "Les Cars" is still operating, and consider taking it to Charles deGaulle/L'Etoile (the Arch de Triomphe), at which station you just take the Metro (Line 1, I think) which will be a straight shot - 1 or 2 stops - to Franklin Roosevelt. You could even think of a taxi for that short ride down the Champs Elysees. Incidentally, the Air France coach gives a discount to a party of 4 traveling together. Of course, for 4 people, a taxi directly from the airport could possibly have a competitive price. Just something to consider.

I just noticed that there are actually 3 of you, so please disregard any statements in which I allude to 4 people.