ScottTexas, If it were me on that short of a stay I wouldn't buy any passes, especially if you plan to take advantage of the free museum Sunday. You would have to spend a lot to buy a transport pass for extended zones to take you from the airport, to center, then out to Versailles. Buy a carnet of 10 tickets and pay for the train RER as you go. Then you have some flexibility. You and your mother may enjoy a nicer way of getting from the airport to your accommodations then the RER.

Bercy is not far from my favorite Paris food area--Chinatown. Get off at Place d'Italia Metro 6 and walk south, make a large triangle back to your origin. If you prefer spicy, healthier food, the choice is amazing and very reasonable. IMHO French food is generally boring. You can jump back on Metro 6 to take you to the Eiffel and the Arc. Also, Metro 6 can drop you off at the Eiffel for the river cruise which is a great way to see the layout of Paris and the lights in the evening. It leaves at 6 pm and the cost is nominal.

You are well located to transportation and should be able to get about easily.

All of the above are dependent on the weather which has been freezing of late.