Transfer from CDG

Paris cab rides from CDG are a set fee now. To your hotel would be 55 Euros for the two of you. There's less expensive ways to do it, certainly, but if you think you're going to be too groggy, then just grab a cab at the airport.

Yes, Paris Museum Pass is sold in many locations at the airport...very easy to find.

Best is relative! It's so much easier to take a cab! You need to go to the official cab rank at the airport. Some people indicate they have been approached in the terminal asking if they want a cab but if this happens to you ignore them and make your way to the official line. The night before you leave ask your hotel desk clerk to arrange a taxi for you. They are very good about that.

Have a wonderful time!

None of the bus or Metro options are direct to that neighborhood - all require a connection (see p. 519 if you have Rick's Paris 2016 book).

We used a private transfer called Interservice Prestige. They picked us up at CDG and took us right to our apartment for 50 euros. It was super easy and I will never do it any other way. You can easily get your Museum Pass once you get to Paris. We bought ours near St Chapelle, at a tabac. Have fun in Paris!

Thank you everyone for your recommendations. Seems like a cab is the way to go.

You can arrange a taxi yourself for the return trip to the airport at the same price, using this reputable Parisian taxi company. Book online or by phone in English, and be outside waiting 5 mins before your scheduled pick-up time.

In addition to the flat fee, there's a 7 EU fee for booking ahead, but this might be far less than the hotel charges you.
https://www.g7.fr/en/

We always just go to the taxi stand and get a cab on arrival from long flight... much easier and worth the cost to us. :)

The tourist information center in the airport is easy to find - just look for the overhead signs.
If you're too tired when you arrive, you can purchase the PMP at the first museum you visit. It's a good idea to choose a museum that won't be too crowded, though. Invalides and the Conciergerie are good choices.

Another vote for an official taxi from CDG. I used to try to save a few euros and use van services but ran into some problems over the years (late pickup, couldn't find my address, etc.). I now use taxis and have no worries, especially now that they have set fees!

Is the set fee good for 4 people in one cab? I will be travelling with wife and 2 teenage sons (packing lightly). Can 4 people and bags fit in a standard cab?

The flat fee is for 4 people plus luggage. The dispatcher at the head of the line will match you with an appropriate cab. There are van cabs as well as sedans; 4 may fit in a sedan but they will probably put you in a van cab.