4 hours in Paris with wheeled carry on

Except you won't have 4 hours in Paris. It could take a hour to clear passport control and get your luggage, then exit the airport. Figure a minimum half hour to get into Paris by taxi- you only have 2 1/2 hours to spend. And I would think you would want to be in the station about 1/2 hours before your train departs.

Perhaps find a nearby sidewalk cafe or restaurant for a leisurely lunch? The Parc de Bercy is close by if you would like a fresh air stroll. I assume you mean the Gare de Bercy?

I agree with CJean. You really don’t have as much time as you might think. You might have just enough time to grab a croissant before hopping on the train.

Bercy not Bursey does not have lockers. -- It will take you about 60-90 minutes to get out of the airport -- and an hour to get into town, so find a cafe near the station and get a little lunch. You really wouldn't have time to check in luggage and then get it out again and do anything interesting in the time you have anyway. If you aren't ready for lunch, use the time to pick up sandwiches etc for the train.

A Saturday morning at the train station in Paris will be busy. August is the month Parisians typically take their own vacations. Get there early.

There's nothing at Bercy or nearby. Cafes are few. Food to purchase is almost non-existent. This used to be a cargo train station. My in-laws lived on that train line and it's a long, slow slog to get down to Beaune on the local train. You might like it because it will be new to you. Local trains have no seat reservations, so get their early. Saturday noon in August is not the worst time, Saturday morning is, but with no seat reservations, if it fills, you could have to stand. It also won't be air conditioned. My choice would be a TGV to Dijon and then the local train to Beaune. Friends who live in Beaune tell me there's one train diretly from CDG a day. And there are trains to Dijon from CDG.

However, leaving from Bercy, to get food, you could go from CDG to the Gare de Lyon. Take a look at a couple of things if time allows: Le Train Bleu restaurant, the wall murals, and then buy some sandwiches and drinks to go from a vendor. From Gare de Lyon, it's an easy walk to the Bercy station.

Bets, the food situation around Bercy station has improved a lot; there are a few to-go options at the station, and a handful of eateries in the block opposite the station (down the ramp or the stairs).
Also, even though the rolling stock on the line from Bercy to Beaune is made of old "Corail" cars, it is air-conditioned (with the odd malfunction from time to time).

In any case, with 4 hours between landing and train departure at Bercy, you will not have time to stash your suitcase and go anywhere else. If you have a spare hour, you could wait in Parc de Bercy for a bit, but that's it.

So they've put the old Corail cars on that line. If I remember correctly, the windows don't open if the air conditioning isn't working. But they are a step up from those screechy old cars, where each time they braked, you could smell metal inside the car. Glad to know the food situation has improved.

Are there trains from CDG to Beaune? Although it’s not the answer to your question you may see if that’s an option.