How to go from CDG to George V?

Since most of your travel is happening during the week, it would still be worth it to purchase a Navigo Decouverte pass when you arrive on Friday (even though you cannot use it till Monday).
 
For your initial travel to from CDG to Champs-Elysees you could purchase single-use RER tickets (total cost 40€) and take the RER B from CDG to Paris Chatelet les Halles, transfer to RER A direction Cergy le Haut / Poissy / Saint-Germain-en-Laye (either of the three) until Charles de Gaulle Etoile station (at Arc de Triomphe), then it's a 10 minute walk down Champes-Elysees to George V.  An alternate which does not require as much walking from Arc de Triomphe to George V on the street, but requires a fair amount of walking at Chatelet les Halles station, you could transfer from RER B to Metro Line 1 direction La Defense until Metro station George V.  Please keep in mind that although the RER to Metro transfer sounds more direct than RER B to RER A, it's more complicated within the cavernous Chatelet les Halles station to transfer from RER B to Metro 1, than RER B to RER A.  If you keep your eyes on signs for Metro 1 (yellow colour) within Chatelet les Halles, you'll eventually find the platform.
 
Another option you may consider is simply taking a taxi from CDG to George V since you are four people with luggage, the 60€ price (approximate) may be worth the extra cost.  It would also likely be faster unless you are traveling within rush hour.