Experience with Paris City-Line Shuttle (or any other shuttle) service?

that is cutting it enormously close; I doubt you will make this train. Everything has to go perfectly to do so. I would not chance it on a shuttle which is the slowest and least reliable way to get into the city. It takes about an hour to get through immigration at CDG (you might get lucky but you might also be behind 3 other jumbo jets). It takes about an hour to get into the city. With this many people a cab will be most efficient and probably cheapest. It is roughly 50 Euros to St. Lazare plus 3 Euros each for every passenger above the first 3 and a Euro for each bag in the trunk. It is unclear how many you are, but assuming 5, a cab will probably be cheaper than a shuttle. Shared shuttles are very slow and stop in many spots. They also often don't show or are late -- you can't afford to lose a second. The cab dispatcher in the official queue will match you with a cab that can't take all of you and this will be your best bet.

If you can book the train later do so; if you have bought the tickets you should be prepared to buy expensive walk up tickets if you miss the train which will happen if your plane is half an hour later or there are any unexpected delays.

That is what I call liking to gamble.

Much like janet travels I don't think you will make it either, even if everything goes your way unless your plane is extremely early and nobody is in the border control queue ahead of you and you have no luggage.

You don't say what time your flight is expected to land. I hope it isn't in the morning rush hour.

I have a similar question. We are a party of 5. Each person will have a carry-on bag--we're packing light. We're not particularly concerned about time, just finding the least stressful way to get from CDG to Gare St. Lazare with 3 inexperienced travelers in the group.
We've seen conflicting information about whether 5 people can take a single taxi. Some sources say the dispatcher will get a van, other sources say you have to take two taxis. We really don't want to split our group. By ourselves we'd normally do public transit, but it seems like an intense and stressful option for folks who've not experienced it and who will be sleep-deprived after a trans-Atlantic flight.

It is extremely common for there to be groups larger than 4 at the airport and you will have no trouble getting a single cab to take you into the city; get into the official queue and have one person let the dispatcher know you are a party of 5 -- they will match you with a van cab. This is just no big deal at the airport. The most that will happen is that you will have to wait a bit for the right size cab, but dispatchers deal with this all the time.

Two hours--not a chance if it's an overseas flight. It may be possible if it's an interior EU flight and you don't have checked luggage to collect. You should change your tickets if it's a non-EU international flight.

We go yearly and it typically takes three to four hours from the moment we touch down to the time we unlock the apartment.

Why? CDG is huge. Your plane may taxi forever in what seems like circles. You may be in the back of the plane. You may have to ride a bus from a landing strip way out to the terminal. The walk to passport control in the terminal may be long. The passport lines could be filled with a jet from China, another from India, and yours at the same time. The walk out to the luggage area could be long. Luggage may take time. Traffic into the city could be jammed due to rush hour.

If you have not yet bought tickets from Paris to Bayeux, then I would wait and buy them in the station for €40 per person, instead of the non-refundable advance-discount rates.