The Navigo weekly pass is valid from Monday through Sunday.
So, yes, you would be able to use it to go from Paris to Roissy/CDG airport on Saturday.
You would just have to use individual tickets on that Sunday when you arrive in Paris.
Or do some sightseeing in walking distance of your hotel.
You also don't have to wait until Monday to buy the Navigo pass. You can already get that done on your arrival day at any metro or RER station.
Just bring one passport-sized photo for each person.. the staff will clip them to fit the Navigo pass.

So far, I have never used anything but public transport to get to/from either Paris airport to/from the city.
Depending on the location of your accomodation, you could think about using a taxi to go from there to the nearest RER station as navigating the metro system with larger luggage can be a bit strenous (stairs).
Or take a bus to the nearest RER station.. but it depends a bit on where you will be staying which option would be more feasible or convenient.

Cowboy,
I would avoid the subway (especially if I needed a transfer) in NYC with bags. That's because our subway system is old, with no escalators and I can't imagine carrying a bag up and down the stairs; although I know a lot of people do it and survive the ordeal.
All I know is that Paris metro is very nice and easy to navigate - does this mean escalators?

Nothing booked yet, but I think the top contender for our hotel stay is La Perle https://www.hotel-paris-laperle.com/fr/ with several metro stops near by, but requiring a transfer to the blue line that goes to the airport. Do you know anything about escalators in Paris?
Thanks

Don't count on finding escalators. And try to remember that the Metro lines are not named by colors, which can vary depending on whose map you are using.

This site tells you which stations and lignes have escalators (wheelchair access means a lift) but even in stations with elevators you may have to go up and down a few steps:

https://parisbytrain.com/map-paris-w...-rer-bus-tram/

Paris buses are a good alternative to metro - no walking long distances to metro stations and once in them - and for short distances more likely to let you off right near where you are actually going. And you can see Paris as your bus rolls along - metro stations and trains can always be chock up with many standees - especially at rush hours so buses can be more comfy and less likely to be crowded.

Walking in Paris can be a joy - stop at an outdoor cafe and watch the Parisian world strut by. I always thought that what I saw when walking between main sights was often as interesting as the sights themselves.

I especially enjoyed taking the above ground metro lines - from which you can see the neighborhoods the train goes thru and tall landmarks of Paris - these lines were especially delightful at night when the neon lights below on shopping streets were sublimely illuminated and you see the locals milling around. I've just taken these lines sometimes with no real destination in sight. If you plan carefully you can practically encircle inner Paris by elevated metro lines, such as these three lines:

https://www.spottedbylocals.com/paris/metro-line-n6/

https://www.pariscityvision.com/en/paris/metro-line-2

https://www.pariscityvision.com/en/paris/metro-line-5

Paris has two major systems of rail mass transport.
One is the Metro (lines are numbered) which is (with some exceptions) old and similar to the NY subway. Stairs, and just a few escalators here and there. Not recommended with big bags or suitcases.
The other one is the RER, fairly new with wide trains and many stations accessible also by escalators and elevators.
If you should stick with that hotel "La Perle", your nearest RER station to get to CDG airport would be St Michel (near Notre Dame).
It does have an elevator, just so well hidden that no living person has ever found it.
The other RER station would be Luxembourg, but that's one of the few that has no elevator.

If I wanted to catch the RER from the La Perle hotel, I'd take a taxi to Port-Royal RER station.
It's somewhat further away than the other ones, but has the advantage that it's just the line B you want to get to CDG. And that station has both an elevator as well as a simple layout. And is not really deep underground.
Port-Royal has an easy to identify station building in that intersection, and the elevator right next to it.
https://goo.gl/maps/zbYFNdasWdL2

Have I told you all how much I appreciate all your help? You are the best, thank you! This is fabulous info that I couldn't have found in any guide book or by just google-ing it.
This is going to be such a great trip :)

I don't use the metro much, prefer the bus or walking, but the last time I was in Paris, the one time I used the metro, the escalator was not working and had to walk up many stairs...just so you know that might happen.

Like Cowboy, we have always used the RER to/from CGD...but we travel only with two carry-on bags and get off at either St-Michel or Chatalet-Les Halles, both of which have escalators (as does CDG).

If you have regular-size bags, and are going to a station without escalator, you are smart no to take RER...unless you are young and strong. :)

...but all the great things everyone has said about the buses and the Navigo pass are true. On our first trip in 2001, we used its predecessor -- the carte orange and have never changed our opinion, even when we only could use it four days of our trip (because of the Mon-Sun rules.) I'll summarize what all have said:

• convenience of not having to constantly buy tickets
• the pleasure of riding buses
• advantage of hopping on for short rides when tired without "counting" your tickets
• not worrying about wasting a ticket if you get on the wrong bus -- which WILL happen
• getting on any bus if "lost" and watching out the window for a metro station
• the fact that a bus-metro ride requires two tickets
• the fact that it includes all zones -- you might change your mind about going to Versailles or decide to go somewhere beyond zone 2.
• ...and finally, two things and not to be minimized:
  • the coolness of having your card as a great souvenir.
  • the card has no expiration date...after one visit to Paris, you WILL be back, and you'll be able to load another week pass at a self-serve machine at CDG...really convenient!!!

ssander

ssander,
Great reasons for the Navigo pass, and it looks like good option for our Sun-Sat stay, especially if we use it to get to CGD.
LOL, "young and strong" we're not but there are some very good options here on how to get to CDG cheaper. I think we'll be fine :-)

When you use the Navigo, be sure to tap in on the pad once and ONLY once. I had used the metro many times, but things had changed....15 years since my last trip. The first time I used the Naviago I was not certain it had worked. I used the Oyster Card in London and when you tap it the "gate" opens, but it's different in Paris. The gates don't open but are "released" so you just walk through them. I tapped, didn't think it worked, tapped again and what do ya know....LOCKED OUT!!!!!! NOOOOOOOO, what to do what to do.

I very nice lady let me cut in right behind her since my travel companion was much smarter than I was and only tapped once and walked on through. The "lock" makes sense because it prevents someone letting 10 of their closest friends though on one Navigo. Too funny. So glad someone took pity on me. Anyway, don't make that mistake. I loved the Navigo, we used for Versailles, and Fountainbleu. So convenient. Yes, stairs, stairs and more stairs. I had thighs like rocks by the time I left for home.

Ohhh, good point, crefloors. Makes sense why it works this way, of course
Paris Voyage

But if we mess up, it's only a 5 minutes wait - it won't kill us.