First off, I've not been to Paris, but I love to travel and have my own mobility issues, and understand liking to be rather near to train stations and bus lines.
I'd say get a very good paper map of the city, one with all the small streets listed, with clear indications of where the subway stations are, and preferably if the map shows the city's many arrondissements, the museums, churches, and so on. Even though those kind of paper maps are fairly large when unfolded, you may be glad to have it with you at some point. You might not always take it with you, but it can be good to have in front of your face instead of a smallish computer screen.
You will have other info with you, maybe via your smart phone, or one favorite guide book. On guide books, I have gotten along without guide books with photos, instead preferring information. I used to like the Richard Saul Wurman guides on big cities a lot - for the information on what you are seeing as you go through different neighborhoods.
Also, your hotel will probably have a simple but helpful local small map, to have in a pocket.
Lots of people on a2k like to travel, many have been to Paris, and lots of us love food - I'm hoping people will see your post and suggest good areas for restaurants. It would help if people know what kind of food you two might like..
Oh, and have fun, even with the planning part of the trip.