Jen,
Even if you were curious about explaining the "life expectancy" to him sometime in the near future, I don't think you are wrong for asking a question although I understand that is not what you were asking. Of course you are not God and you don't know when his "time will be up", but as emily and some other posters said, he has every right to and should be informed of that and it isn't too early at age 11 to start discussing something like this that can be put in terms for someone that age to understand. Just think of if he hears the life expectancy statistics from somebody else and finds out you knew but never told him. What was told to my husband when he was younger, about 9-10 (back in the 80's) is that "the AVERAGE life expectancy is 18 years, but there are people who live much longer than that" There is even testament to that fact on this board, people who are 40, 50, 60 and such.
And of course as a mother (and personally a step mother is a mother to me) you would never do anything to hurt him, but sometimes the things you are going to have to tell him will hurt, and he might get mad an upset with you. But down the road the scars from that experience will be much less than the scars if you didn't tell him and somebody else did.
As others have said, it's a personal choice but CF camps are discouraged now because of the knowledge about passing bacteria, and even clinics are so germ conscious as to make CF patients wear masks as a preacaution for themselves and others-but there are other options nowdays as well. this internet site, research on the web, and lots of teens on this site under the teenage category ask for pen pals and such. He might resist the idea at first but keep presenting it to him periodically and let him see you on this site, explain that you are doing it so you can understand better and to help him-stuff like that. He will eventually warm up to the idea. I know my husband (who has CF) hated the fact that I came to this site at first, but now he will sit down with me and read with me and when I post somethign he will say "oh, write this" or "ask this question". I don't think he ever initiates to come on his own but he will look while I am on.
The level of what a child can handle and what he still believes in is also a good indication of when they are ready for more serious talks. I ditto what Luke said in the fact that the approach he suggests might work for some children, while others would benefit more from the facts from the get to. I was always a child to ask millions of questions, but if I was really, really curious about something I was kind of embarassed and shy to ask. Why, still to this day I don't know. But those were the times when my parents stepped in and said, "you are getting to that age where you are probably curious about....... so we should talk about it". Some kids need that approach. Ultimately, you know your own childs needs and ways of learning and readiness best.
There are some good CF books out there that explain things too and you should be able to get them from your CF clinic, but if not the cff foundation has some. I have a good one provided by Solvay Pharmaceuticals Inc called Growing older with CF, and handbook for adults. Even though it says adults, everything in that book is explained in laymans terms so I think most teenaged kids would be able to grasp most of the things in the book. And the things they don't understand would be good starting points for discussion.
I also agree with everyone else who said, don't push it too much. Let him know you are here to talk, answer questions and periodically ask if he wants to talk and read some CF related things with you. But if he is "standoff-ish" about it, give it some time before you ask again. He's approaching his teen years and even without the CF factor, they are very difficult times nowdays, believe me I am not that far removed from that time.
Best of luck and don't ever feel bad for asking a question, even if somebody else tries to tell you it's bad (or whatever was said) you have questions that need to be answered and the bottom line is that sometimes the truth hurts but it needs to be told by someone. if you ever need to talk off this site, I can email you or have my husband email you if you want to talk to an adult CFer.
Julie (wife to Mark 24 w/CF)