Basically because of cross contamination concerns and the bugs they may carry -- pseudomonas, cepacia, mrsa... cfers should maintain a distance, not be in close contact with each other. Lot easier when your child is older, but with youngsters, especially toddlers who always have to touch things, do the hand to nose/mouth contact... I believe the CFF has pamphlets on germ prevention, CF in the classroom -- one of those mentions not having cfers who go to the same school in the same classroom.
Our local cf clinic has a community waiting room, patients go from room to room to see the medical staff, and not the other way around, there are toys in the waiting room. They're not concerned with the cross contamination issue because none of their patients have ever cultured cepacia at their clinic.
Our clinic STILL doesn't encourage doing CPT or the Vest until their are lung issues. I just spoke to a parent of another CFer, who like us goes to a different clinic in the City rather than the local one and she told me about a family in her town with two teenagers wcf who go to our local clinic and the eldest one JUST got a vest, the youngest doesn't do CPT because "her lungs aren't affected".
Oh and ditto on the hot tubs. After reading a recent article in the paper about the millions of particles of bacteria in those things, I don't believe I'll ever set foot in one of those again either. Hotter water has the potentional for growing more things than say the cooler water in swimming pools, plus when you're sitting in a hot tub, the steam is probably at face level, so you're breathing all that nastiness in. DS does go to swimming lessons, swims in pools and lakes.