Thanks Travelnut. I wondered about that tram line and appreciate the tip.

I am trying to remember from our visit two years ago if one of the Orange Cards gives us the ability to ride all the public transportation - Metro, RER and busses. Is this correct?

Yes. They are in process of phasing out the paper tickets, so don't be surprised if you find you need to buy the electronic pass (plastic card) - 5€ one-time fee to buy the card. Then the 16-17€ to load the 'pass' for zones 1-2, and remember it is only usable from Monday-Sunday each week. And you need the little 1x1 inch photo for the id card.

Another option is to buy a daily pass called Mobilis, which is at/under 6€; no photo required for that one. You can buy more zones for higher price if that works for you.