In reply to tony:
> Depending on what time you arrive on Friday, Notre Dame would be top of my list, along with the Towers of Notre Dame. You may have to queue, especially for the latter.
You can jump the queues to get in by joining one of the tour groups - find an English/American one outside and come back at the stated time. Once in, you don't have to stay with the group.
If you want to do the Louvre, get there very early, as that has long queues, even with pre-booked tickets. Doesn't look like it'll apply to you, but, for anyone else reading, if you have a pushchair, they let you in a side door and you can jump the queue that way.
Depending on where you're staying, the area around Bassin de la Villette is quite chilled in the evening. Camarade Boris is quite quirky and does good food.
As you've got bikes, you could always have a pootle along the last few miles of the Tour stage. Sacre Coeur also good to get to by bike - pain by car! Good views over the city.
Paris Catacombs?