Travelled with my wife and our two kids, 14 and 12. We rented an apartment in the 7th right near Ecole Militaire metro / Rue Cler. We hit all the highlights:
1. Tour Eiffel - went to the top, worth it but go during the day, we went at night. Day better for photos and seeing sights. Line took about 30-45 minutes to get on elevator.
2. Louvre / Tuileries - Beautiful museum but pick what you want to see. You could easily spend 3 days there but after a while everything begins to look the same.
3. Invalides - I would skip the war museum unless you are a war / weapons buff, it was alittle dry. The tomb of Napoleon is great, get the audioguide!
4. Notre Dame - Nice church, alittle overrated but nice. We walked in but did not go to the tower as the line outside was about an hour long. We also visited both islands and had the Berthillon ice cream.
5. Sacre Coeur - Great area for shopping and restaurants. Nice church with a great view.
6. Champs Elysees / Arc de Triomphe - Wandered around, expensive area to shop and eat, beware! My son just had to buy a Lacoste shirt he could have easily bought cheaper in Canada but it was his money!!
7. Catacombes - This was cool, my son liked it but not sure if walking through a dark tunnel with bones piled up is worth 35 euros but we paid it anyway. Very quick tour, only took about 30-40 minutes.
I would say we enjoyed the Latin quarter and the area around the Sacre Coeur the best. Lots of restaurants and cheap shopping. My sone also liked the area around Moulin Rouge but for different reasons!!
We used the Metro and the RER and never had any problems, very easy to get around. We bought the 5 day pass and it was worth it. We ended up taking a cab to the airport when we flew to Venice as the trains don't start early enough depending where you stay in town. Make sure if you book an early morning departure, you make other travel arrangements.
Depending on what country you come from and how your dollar compares, be prepared, Paris is ridiculously expensive. We also toured London, Venice and Rome this trip and Paris was the worst, cost wise, by a mile. If you eat in the areas I mentioned above, you can save some money. Stopping at a cafe for a drink (no food) beer, wine and two Cokes will easily be 25 to 30 euros.
Of the four cities we visited, we all agreed, Paris was the best. Lots to see and do and so much history. Our only complaint would be that the city is pretty dirty. Seems to be the thing to discard your cigarette butt wherever you want as the streets and sidewalks are filled with them. Perhaps if someone knows anyone on their city council, suggest installing some trash bins around the city, they are very hard to find so people just toss bottles, butts, paper, etc anywhere. Paris is such a beautiful city and the garbage certainly diminishes the shine abit.
If anyone has any questions, let me know, I'll do what I can to answer.