I just want to add my experience with PICC lines (before I got my beloved port!):
I tried to work out once, and by the end, the insertion site was leaking blood and obviously required a new dressing. The picc was still working, but I was kinda freaked out by the blood.
Also, the line can move without a great deal of activity. The nurse measures the length of the line outside the arm, and if that length "grows", the picc is no longer in the right place. I was VERY protective of my Picc lines (especially after the bloody-workout!) and they would still move over time.
I know it sucks to have to cut out recess and phys-ed class, but it might be a necessary sacrifice.
I know this might sound weird/harsh, but I wish that my parents didn't make me think that I could do anything/everything just like everyone else. I believed that, and so I found it harder to cope when things didn't work out for me because of CF, like when I couldn't keep up in gym class, or when I missed my high-school graduation. I wish that I had learned to accept my differences/limitations so that I could embrace my CF to a better degree, so I could live with CF, not in spite of it.