We will be arriving in Paris on Sunday in a few weeks at 11 am. We leave for Lyon the next morning at 8 or 9 am. Should we book a hotel close to the train station to avoid traffic on Monday morning or is it fairly easy to get to the train station if we get a room close to the Eiffel Tower?
It is fairly easy to get to the train station if you take the metro; but it may be uncomfortably crowded and you have to squeeze in with you baggage; a taxi may get caught in traffic.
If you stay by the Eiffel Tower, you will have to make at least one change on the Metro to get to Gare de Lyon.
Where are you arriving in Paris? CDG? Gare du Nord? I think I would probably stay by the station to make it convenient on Monday morning. It's only one night, so it's not a big lodging decision. You really can't go wrong.
Since you're only there for one night, I would be more inclined to stay a walkable distance from the train station, and that was my choice in a similar circumstance. If you need a taxi, bus, or metro to aid your sightseeing on your free afternoon and evening, you would at least be under less pressure and not carrying luggage.
While a €55 flat-fee taxi ride is the easiest way to come in from Charles de Gualle airport to a hotel near the Eiffel Tower (e.g., Rue Cler neighborhood), Gare de Lyon can also be easily reached by line 4 of Le Bus Direct.