Just back from there myself, albeit with slightly older kids, 3 & 5. Had a fantastic time with them.
Day 1: the Eiffel Tower etc
Day 2: the science museum, had to drag them out of it
Day 3: the aquarium and a boating lake in some municipal buildingd
Day 4: Disneyland
Day 5: back to the science museum.
Man, that science museum was the highlight for the kids. There were various hands on activities, starting at 3-5yrs, just perfect for my pair. What a resource, there is nothing vaguely like it in Ireland. I did have the advantage of staying with my sister who pointed me in the right direction. I subsequently discouvered that the Pompedu (sp??) Center would have been worth a look, maybe next time.