Accessible route from Choisy-le-Roi to Stade de France

I was hoping to give you multiple options of varying time & levels of assistance/planning needed, but after a couple hours of research, I've only come up with one fully autonomous self-accessible route and another that requires assistance from station staff, by telephone reservation, 24 hours in advance.
 
The reason for the limited solutions is that the vast majority of the RER C line stations are completely inaccesslble by wheelchair (they have stairs to/from platforms and there are no elevators), including one key station you would need.  To get from Choisy-le-Roi to Stade de France involves a transfer from RER C to RER B (at Saint-Michel Notre Dame) which has no elevator access for the RER C side of the station, making this route impossible.
 
RER D line is not much better, requires station staff assistance at both ends, and the arrival station is significantly farther away from the 2nd solution below.  So I haven't included that solution either.
 
So here's the first solution that is fully autonomous.
 
Bus 183 - Metro 14 - Bus 173
This route takes 1 hour 40 minutes and is fully self-accessible/autonomous.  No help from staff needed.  Elevators at all level changes, wheelchair accessible fare gates, roll-on, roll-off both kneeling buses & Metro 14 train cars.  (Metro 14 is the only fully accessible line in Paris.)  Instead of taking RER C at Choisy-le-Roi you'll take Bus 183 in direction "Aeroport d'Orly 1-2-3" until "Thiais Pont de Rungis" (12 stops away, ~23 minutes). This bus stop is at Metro 14 station Thiais Orly. (Check the elevator status at Thiais Orly here.) Here you take the Metro 14 in direction Saint Denis Pleyel until station Mairie de Saint-Ouen.  Take elevator to street level and find bus 173 stop "Mairie de Saint-Ouen - Jaurès".  Take bus 173 in direction "La Courneuve - 8 Mai 1943" until La Plaine - Stade de France RER.  From here it's an easy walk/wheel to Stade de France.
Using Google Maps "street view" you can get your bearings at street level, for example to navigate to the bus stop at Mairie de Saint-Ouen - Jaurès.
 
Below is the only other route that I think is feasible, but requires station staff assistance at both ends of the train section of the journey and one of those (at arrival station) requires 24-hour advanced notice by telephone reservation.  It's only slightly quicker.
 
TVM Bus - RER B
Total travel time 1 hour 20 minutes.  24 hours before each day's departure, you'll need to make a reservation for wheelchair assistance at the arrival station of La Plaine Stade de France.  (Check elevator status here.  You'll need both elevators working since one is for the northbound trains, another for southbound (your return route) trains.)  See the telephone reservation instructions (English in light blue italics) on this map, under "Accessibilité" / "Gare accessible" to make your reservation.
Start by taking TVM bus from Choisy-le-Roi in direction La Croix de Berny RER until the final stop/terminus of La Croix de Berny-RER.  From here you'll wheel to the RER station of the same name.  You'll need to request assistance from the ticketing staff / station agents for boarding the train (no reservation needed).  You'll be taking the RER B train in direction Aeroport Charles de Gaulle (which will pass Stade de France on its way) and your destination station is "La Plaine Stade de France", not "Stade de France Saint-Denis".  "Stade de France Saint-Denis is on RER D line.  You want "La Plaine Stade de France" on RER B line, which is both closer and doesn't cross an 8-lane freeway.  A staff member will accompany you to the platform with a foldable steel bridging ramp to bridge the gap from the platform edge to the train door when the train arrives to allow you to roll aboard.  They'll likely do this at the head train car (attached to the driver's cab) and they'll let the driver know you're going to La Plaine Stade de France.  This way the driver can coordinate with the arrival station staff which will need to assist for alighting using a ramp to bridge the door-platform gap.  Your telephone reservation the day before will ensure there's station staff at La Plaine Stade de France to help with this.
When the train rolls into La Pleine Stade de France, the driver will likely pop his head out the window or out his door to monitor your assisted exit from the station staff who will be waiting at the lead train car positon on the platform to deploy the bridging ramp.  They'll then guide you to the elevators where you'll ride up to street level.  From there you can wheel to Stade de France.
 
So, those are the two routes I came up with.  Keep your eye on the elevator status pages linked above for your stations.  You'll want to see green check marks before beginning your journey, otherwise you'll need to find an alternate solution.
 
Since you're staying for 11-days the Paris 2024 Pass (on your mobile phone via Paris Transport app or Apple Wallet or Navigo Easy) is your best option price wise & convenience.  When bought as a 7-day pass (the max), it'll be 10€/day.  If you tried to use single tickets the cost one-way of bus + Metro + bus would be 12€ so 24€/day or bus + RER for 10€ one-way or 20€ per day.  And RER tickets are not available in electronic format so must be bought from ticket windows / ticket machines.  You'll need to renew your Paris 2024 Pass on your 8th day to cover days 8, 9, 10, 11.  The price for four days is slightly more at 13€/day due to the shorter duration.  Still your best option though.
 
Here's a hub of information regarding accessible transport in the Ile-de-France region from the regional transport authority that's useful.
 
Hope you have a great Olympics visit.

One other note: on your first day, August 1, bus 173 has several stops that are not being served, one of which is La Plaine Stade de France, so if you're using the fully autonomous route I provided, for the bus 173 part from Mairie de Saint-Ouen you'll need to alight at the next nearest bus stop of Murger.  From Aug 2-11, bus 173 follows its normal service route/stops so you'll be able to alight at La Plaine Stade de France (to closest stop to the stadium).

Actually, I read that service update wrong, the deviation in route is from Aug 2 to Aug 10, pretty much your entire stay, so you'll need to use bus stop Murger instead of La Plaine Stade de France.  Sorry, I didn't see this service update till just now.