Starting off on the first. If your school has a good music program each student gets an instrument (or rents one through a company) at the beginning of the year until the end of the year. (I know my school did this) the instruments were inspected and cleaned before being given to students, in anycase all of them were taken out of the band hall and given a thorough inspection at the end of the year. That being said if you are worried as the band instructor.
'I would suggest that the smaller instruments like the flute would need less lung capacity to use. '
Sorry but wrong wrong wrong wrong wrong and why? If you're going to take an instrument why not try to get out of it all that you can in the first place. I mean yes I know it's up to the person potentially playing what they want to do but why restrict yourself (or somebody else) because you feel they can't? My band director did that to me and I chose the flute to spite her, and I became good at it, very good at it.
Out of all the instruments in the band the flute probably takes the most lung capacity to play. In fact I was warned against trying the flute because it took so much air capacity, and would work my lungs beyond what the school band director (at the time) thought I could handle.
With the flute you are not pushing air into a mouthpiece you're expelling air from your diaphram. In the correct musical setting taking a breath every few second is not permitted and makes the music sound bad particularly if you are playing in a concert. They have things like 'rounds' prevent this even, so certain people are permitted to breathe at certain times. Learning how to control your breathing to get certain sounds, and how to channel your breath is great for your lungs. I know when I first started playing it helped me with PFTs just learning how to breathe properly. (For reference when I was listed my FEV1 was 32-42%, and stayed there for 3 years, I credit it to playing an instrument). It makes you work, but it's worth it.
'your boys don't have too much lung function, so I would NOT suggest the flute, because I know it takes tons....'
sorry but i'm going to say this again.
No.
Wrong, not a good recommendation (sorry Allie)
When I first started playing the flute it was hard, mostly because I did not know how to get the mouthpiece turned just right to make a sound. Then conditioning your lips to hold that position (embouchure) wow not fun. But I credit the flute to maintaining my PFTs for quite a few years. Naturally I was on a downhill spiral due to having caught MRSA, but I credit the band for keeping my PFTs up as much as they were. I never coughed up so much crap as when I did after band practice. It exercises your lungs and keeps you breathing. Yes it makes you work tons but you build up to it and it is sooooo worth it. When I first started playing the flute I was 13 or so I was listed at the end of 13 for transplant but my numbers stayed steady. I didn't really start to go downhill until I built up a resistance to everything but vanco (late 16-17-ish)
'Woodwinds and brass instruments in many cases can help improve lung compacity.'
Bingo!
I don't care how low your lung functions are but it definitely can't hurt it. The only way it would hurt with CF is not trying something and holding back because it 'might' be too much to handle. Never know til you try.
I know I'm making such a big deal over the flute but a lot of people have misconceptions about it. I know your boys probably wouldn't want to play something girly such as a flute, and that's cool because I know a lot of the instruments have benefits for CFers (even the drums build up muscles and keep you moving). Just try something! Personally I would recommend the flute, and I've said that many many times before on these forums...
I hope I have not offended anybody with what I've said I just hate to see a good opportunity go missing, especially one as beneficial as band/an instrument can be.