I just did this last summer, 2 adults + 2 kids into CDG in mid June, return from MAD at the end of June. Booked it around the end of December 2011. The key was being flexible with my dates knowing I could leave during a specific week and being about flexible about a return date. The biggest problem I encountered was getting from FRA to CDG, not on the TATL flights. All at the lowest level pricing with US.
Now, I actually booked a non-optimal flight set, but was able to switch to my preferred flights because there were schedule changes. I did not count on the schedule changes, but it worked out great for us.
Good luck!