No-the wonders of www-wrong message. Actually -like so many form far over the oceans who think its all like planes: it is NOT. You are waaaaaaaaaaaaaaaaay to early for bookings/RES summer. Accept that 2 month advance was and is for some still the term-and in some cases its a little longer. All those great fears that trains are ´full´ so long ahead is also plain nonsense-it would not make much sense to run any railway for normal daily transport like that.

Also: there are far better-cheaper too ways to make RES once possible-mostly directly via site of  railway (but this is not in FRance-those TGV trains). Others will follow up and provide links to that.

You CAN get a global, not 100% accurate idea, of how lines work-times, how often etc. by simply using any decent planner (bahn.com works best for most of EUR) for sameday next week. F.e. Annecy needs quite a detour, this is not very direct possible on iron rails.

But yes-as such the pass is not (it has never been) valid on each&every train-varies quite a lot per country. But most exceptions are tiny minor branch lines that no 1st timer will use or in some countries newly established commercial competitors on the new hi-speed lines

And another hint if you try to do from US: take care to use a time that is also still same day here in EUR-as the time will be set to that in EUR and that may mean its is already next day if its late PM in USA. There have been several wondering remarks about that. I did not invent that all-I just mention what others have posted

Exactly what routes, dates and departure times are you looking at? What types of Eurail passes do your parents have?

Hello,

your "problem" is that the tlmetable does show all trains running not just these for which your parents pass is valid. There are indeed trains for which it isn't valid. 

Regarding high-speed-trains: If the train shown is named TGV, the Eurail pass is valid. If the train shown is named OGV, the Eurail pass isn't valid (that's a low cost brand, Ouigo, which is less comfortable anyway). You'll see the little difference in name when having a closer look at the timetables.

But that's not a real problem at all. Most trains are TGVs which are allowed to use and it's clearly shown. No need to worry about departure times, trains and routes. Just avoid the OGV trains. 

Regarding the price: A mandatory reservation for TGV trains in France does cost 10 € if there are not many passholder reservations sold and 20 € when the cheaper reservations are gone. Prices are per person and train.

Kind regards, Hektor.

However, Eurail sells all reservations for 20 EUR, even those who actually cost 10 EUR so it is better to buy the domestic TGV reservations at b-europe 

https://travel.b-europe.com/eurail-ge/en/booking-tgv#TravelWish

If you have a mobile pass you need to generate a Pass Cover Number in order to make the reservation at b-europe. You do that here in the PCN generator:

https://community.eurail.com/news-and-announcements-39/pass-cover-number-generator-is-live-5653