i am feeling a pinch on what to do here.
Only 3 times essentially that depart via train or plane to Lourdes (8am, 1015am 4pm Train) (9am or 4pm flight)
do i gamble with a flexible train ticket and book the 1015am train
(pay a little more-THEN pay another fee when indeed i do miss train :) )
or maybe i am just stressing over nothing and i could make a 1015 train with no worries.
From the looks of it, you can actually take a train from the TGV station at CDG that will at least take you all the way to Bordeaux. From there you may have to make another transfer or two to get to Lourdes, but at least you won't have to go into Paris to catch a train. If this is the case, you should be able to clear immigration and make your way to the station in 2 hours (granted that your flight arrives on time). If you had to go into Paris to catch the train, you'd be cutting it close. Check here for schedules and fares (be sure to enter CDG for departure point): http://www.sncf.com/en/passengers
As for flights, it appears there are only flights between Orly Airport (which is all the way in the south of Paris) and Lourdes, so a morning flight really isn't reasonable. You could spend a few hours in the city if you don't mind carrying your luggage around if you were keen on seeing a bit of Paris and then head to the airport for the afternoon or evening flight. Otherwise I think taking the train directly from CDG is your best option.
Additional: The Flexible fare is only exchangeable and refundable up to 2 hours after the departure of the train, so a serious delay still means losing the ticket.
If you are going to gamble why wouldn't you gamble and get the cheapest non-refundable ticket instead of the flexible? Odds are you are going to make a 10:15 AM train with an 8:15 AM flight ETA. Standard advice is to allow three hours between ETA and scheduled departure time for your train if you are leaving from CDG and four hours if you are leaving from a station in Paris. You will be paying 56€ for basically two hours of protection.
only book something this tight if you can be philosophical about losing the money. this makes if all goes easily and can easily be derailed by a late plane, long immigration line etc.
Buy the flex ticket. Only do carry-on luggage. When you get to passport control, if there is a long line, show the staff at the first class line your ticket and tell them you have a train to catch. They will usually let you use the faster line. Study the CDG maps carefully so you know where to go. You didn't say which airline you are flying. If it is Delta/KLM/Air France, you'll land at Terminal 2, which is where the train station is. If you land at Terminal 1, you have to take the shuttle train--CDGVAL--to Terminal 2, so be prepared since it's going to take longer. I've made one-hour connections at CDG, but I prepared ahead of time and was lucky my flight wasn't late. With two hours, you should be able to do it if you prepare in advance.
Why can't you buy your TGV ticket after arriving at CDG?
There's a substantial price difference between buying the TGV ticket when they go on sale vs. buying a walk-up ticket on the day of arrival. I did a quick check, and the walk-up price was triple the advance-purchase price (€154 vs. €50).
