Ask your wife to sit on 3rd Floor.
I suggest your guys do together. You can help her a lot.
This is my experience.
I did PP on 1/25/02. Arrive in Federal Plaza at 11:00AM, and get out 2:00PM. The PP room is on 1st floor(room 102) and the line is so long. No seat on the 1st and 2nd floor. There is a big waiting room on 3rd floor. Your wife can sit and wait over there. She does not be in line with you. Once your PP turn coming, then bring her down.
Use escalator to reach 3rd floor. Restroom is on 2nd and 3rd floor.
Good luck.