CDG to Nice

It might be enough. You'd want three to be safe.

It will be a lot faster and possibly less expensive to fly. You are already inside the airport. That's a 7 hour train ride with a connection to a local train in Marseille that has no reserved seats. The flight is one hour with a sensational landing out over the water with the mountains sparkling on the other side. It's a wonderful flight especially with a window seat.

That’s what we’re thinking of flying to Nice. EasyJet only has an early-morning flight on that day. Air France is quite pricey for the three of us.

Two hours is a tumble of the dice, my fellow Canuck. We've opted to fly down on AF then take a TGV back up to Paris later in the month. Note that the latter are both direct to Gare de Lyon and surprisingly costly.
Good luck.
I am done. the transit

2 hours is a bit tight. I'd be more comfortable with a 13:15 train or later. I'd bite the bullet and fly.

As for cost, look into whether you can change your original ticket to include the segment from CDG to Nice. It might not be as much as booking a new separate ticket. And if on the same ticket you will be protected for the connection time.

If you do take the train, check your fare conditions for one that can be rescheduled, if necessary. A flight connection can be easier, but just allow two hours because the AC flights and the connecting AF flights can be in different terminals.

Yes, flying is your better option for the same day. It is a BIG airport.

I checked the easyJet flight from Orly Airport at 1:55 pm to Nice. We will be arriving at CDG around 10:30 am. Is that enough time to get to Orly?

I also checked the SNCF trains CDG to Nice for June 13th, and there are only two options—at 7:17 am and 8:08 am—with just 4 and 6 seats left. But on June 12th and June 14th, there are around nine different trains running. Why?

Yes, only two are showing and they are both being sent out of the way around Bordeaux and across the southern edge of France, about 12-15 hours. Obviously, that's not what you want. Either, trains haven't been loaded into the system yet, or there is some sort of track work that day. The price is ridiculously expensive, too. You are four months out, so there can be changes.

If you want a sure thing, you can bite the bullet and buy the plane tickets from CDG and save money on something else. Or, you can wait to see what trains are loaded in coming weeks from either the airport or the Gare de Lyon in Paris. But remember that this is a six-hour train trip to add onto your plane trip. If from the airport, add 7 hours if SNCF does add a train that take the usual route.

Our train trip home is 3.5 hours. My husband usually prefers connecting to that. When I'm flying US--south of France alone, I stay airside and connect to a plane.

You can always go into Paris, spend the night, and take an early train to Nice the next day.

Transferring from CDG to Orly is a hassle, it should be your last resort.

I found it odd that lots of trains are available on June 12 and 14, but not on the 13th, so I did some looking. It seems that there is work being done on the line between Lyon and Marseille on four consecutive Saturdays.
From the SNCF website, “ Adaptation of the transport plan for direct INOUI TGVs between the North and South-East, as well as longer journey times between Lyon and Marseille/Montpellier, during the following periods in May and June 2026:
From the evening of May 29 to the morning of May 31.
From the evening of June 5 to the morning of June 7.
From June 12 evening to June 14 morning.
From June 19 evening to June 21 morning.
Cause: replacement of switches and crossings on the Line à grande Vitesse Sud-Est.‘
This explains also why the existing options are routed through Bordeaux, instead of the more direct route through Marseille. The Oiugo website also shows lots of options for other days, but those particular Saturdays being blanked out. Looks like it’s either enjoy Paris for one or more nights, or book a connecting flight. Also, having been forced to do the Orly-CDG transfer due to a cancellation of my Nice-CDG Air France flight last month (they informed me 14 hours before my scheduled flight), I would not recommend changing airports.
Edit: I just realized that I didn’t answer your original question about timing, but focused on the lack of options on the 13th. If you are indeed arriving at CDG on a day other than one of those Saturdays, two hours is possible if everything goes smoothly, but you would be setting yourself up for a lot of anxiety if anything does not. I have in past breezed from arriving to the TGV station at CDG in less than an hour, (then waited two more for my train) including passport control and luggage collection, plus walking to the train station. However, if the plane is late or the bags slow to arrive you’d be out of luck. The SNCF website does offer a fairly cheap insurance policy that allows you to switch to a later train if necessary, but if you have the option I’d recommend booking your train to Nice later in the afternoon. (Or better still, fly to Nice.)