Disneyland Paris to Eiffel Tower

As long as you don't leave the Charles de Gaulle-Etoile station, your ticket on the RER A (now officially called Train A, but the signs still say RER) is good for the transfer and ride to Bir Hakeim. You will need to insert it into several sets of turnstiles, so keep it handy and un-crumpled. On arrival at CdG-Etoile, just follow signs to line 6.

However, that just covers the one ride. How many other rides will you be taking in Paris? Will you need to buy other metro tickets, or just the return trip to Disney?

That's prefect, thanks. It's just a one-time trip from Disney to Paris for an evening visit to the Eiffel Tower (bought tix already). So basically, we just buy our tickets at Marne la Vallee and ride the same train all the way to the Charles de Gaulle Etoile station, correct? And those same tickets will get us from that station to Bir Hakeim, so long as we don't leave the station when getting on the Metro line 6.

I'm assuming that when we return to Disney, when we buy tickets at Bir Hakeim it will give us the option for Marne la Vallee as a destination, correct?

Thank you.

I'm assuming that when we return to Disney, when we buy tickets at Bir Hakeim it will give us the option for Marne la Vallee as a destination, correct?

Correct. It is one price from a suburban station (like Marne-la-Vallée–Chessy, to use the full name) to any station in Paris city, and the same price from any station in Paris city back again.
They may not be a manned ticket counter at Bir Hakeim, so be prepared with coins to use a ticket machine.
Within Paris city a so-called t+ ticket is valid from any station to any station.

When are you doing this? I see on the RATP website that the RER A will be closed from July 28 to August 26 for track work Between La Defense and Nation. That will effect your route. You can get the Metro 6 line at Nation and get to Bir-Hakeim that way, but will take a little longer as there are a lot of stops along the way.

How many are going and what are the ages? The 1-way fare is 7.60 EUR per person, and kids 4 to 9 yo get half fare prices, under 4 are free.
If you have 5 or more, you can get a "carnet" of 10 1-way tickets for a 20% discount.

Thanks Chris. This actually feels much more manageable after talking it through.

Sam, we're going in mid June, so we should be ok. Our son is 17, so no dice on the discount, but that's ok.

Thanks again to everyone for their helpful advice.

I'm assuming that when we return to Disney, when we buy tickets at Bir Hakeim it will give us the option for Marne la Vallee as a destination, correct?

No - you can choose and buy round trip tickets when departing from Marne la Vallée. (It will give you two separate tickets, so put the return somewhere you can find easily when it's time to leave Paris!). This will work even if you leave Paris from a different station than Bir Hakeim.

Now, if you want to do some traveling WITHIN Paris after visiting the Eiffel Tower, you will want to buy some t+ tickets. I imagine you can also buy those at the machine at Marne la Vallée, separately from the RER tix you'll be buying to go into town.

Here are a couple of videos that show how to use the machines - and how to change it to English.

https://www.youtube.com/watch?v=K2jqJ9zDf20
https://www.youtube.com/watch?v=UnESfpkyC_Q

For a one day trip to Paris from Disney, I would purchase either a zone 1-5 Mobilis pass or I would load my Navigo Découverte card (if I already had one) with a zone 1-5 Navigo Jour fare. The cost is 17.80€ which includes unlimited travel, until midnight, anywhere on the RER, métro, bus, funicular or tramway.

Take the RER A into Paris, ride the buses or métro anywhere you might like to go, and return in the evening using but one ticket.