I would definitely get a day metro pass for each person to allow you and the family to get around quickly. The metro is clean, safe and very efficient yu can get a map of the metro system online so you can see exactly how to get where you want.
The louvre is an all day place and I have seen the lines with over 100 people waiting to get in. Frankly I wouldn't recommend it if you only have a day. There is so much more to Paris than the louvre. If you must do a museum there are Lots of other museums which are easier to navigate. My favorite is the Rodin museum and gardens. If you do decide to go to more than one definitely consider a museum pass. You can bypass all the lines for most museums, churches, etc. It's only cost effective if you want to do more than two places but the ability to move quickly is the best feature. You might even be able to buy them online ahead of time.
You can see the Eiffel tower from almost anywhere so unless you want to go up it...which again may require waiting in a long line...you Can get great pictures from any bridge along the seine. I would recommend taking the hop on hop off bus to get a good overview of the city. Look them up online to see where to pick up a bus.
Or another idea is to get a tour. Again there are lots of tours to choose from.
Of course I've bern there many times so I have different ideas than someone who hasn't. But my favorite places are
Montmartre, Notre dame, the Latin quarter, the Tuileries and the Pere lachaise cemetery where so many famous people are buried. The monuments are fabulous there and there is a metro stop across the street.
As for food, there is an excellent bistro on almost every corner. Most have steak frittes along with chicken, some have pizza etc. Just remember that a coke or even a bottle of water will cost more than a glass of wine!
I just realized...I must go back! Once Paris gets under your skin it keeps pulling you back. And by the way don't listen to those who say Parisians are rude. If you smile and are polite and don't display some of the ugly American traits we are known for...assuming they all speak English, talking loud, getting impatient...they will be friendly and helpful. I speak no French and have gotten by nicely for several days in Paris with a little sign language, a very few rudimentary phrases and a big smile.