Allowing time from Orly to Gare de Lyon

A taxi might be a good option. You should be at the cab stand no later than 16:00 (if your flight is on time). You might also think about the train at 18:37 if it is running on your arrival day.

Kyle,

That should be enough time to make the connection. Travel time should be about 0H:45M from Antony station to Gare de Lyon (that doesn't include the time on the OrlyVal from the airport to Antony, and as I recall that didn't take long). One route you could use is RER "B" (direction Mitry-Claye / CDG) to Châtelet – Les Halles station, transfer to Metro Line 14 (direction Olympiades) to Gare de Lyon. While it's sometimes a good idea to avoid the Châtelet station due to its size (apparently the largest underground station in the world), this is one of the easiest options and I wouldn't have any hesitation in using it.

Orly is a smaller airport and much easier to navigate than CDG (IMO). There are several transportation options from the airport. I've only used the OrlyVal automated train to Antony station and then RER "B", which works well.

Bon Voyage!

It might be faster and less walking if instead of taking Metro Line 14, you take RER A to Gare de Lyon.

if your flight is on time, you should be okay. If it's not . . . or there's a problem on the RER that day . . .

An advance-discount TGV ticket is worthless if the train departs without you; you'd have to buy a new, full-fare ticket for a later departure. Counting on everything to go right with a short connection sounds too stressful.

You may be better off flying to Marseille. It will get you into Provence much earlier because as it is you will be getting to your hotel very late for check in. Flights leave every two hours and take less time than the train. It will probably cost less as well.

Richard is absolutely correct: fly from Orly.