Here's how I have always replied to questions of this nature and I apologize in advance if it is repetative but I feel the need to say it so...It is a parental instinct to try to and want to protect our children as much as possible but sometimes that can be more harmful in the long run. Consider this, if you are protecing your child all the time now, from EVERYTHING what happens when it's time to go to kindergarden, first grade and so on? If they have been "isolated" for the first 4-5 years of their life and are suddenly put into a situation where every little kid around them has a cold, is sneezing, wiping their nose with their shirt, sneezing on their neighbor, picking their nose...your CFer is going to get sick fast and hard (meaning very badly)- simply because it is such a shock on the body.
If you start gradually introducing your child to the world now, that situation won't come a such a shock to their body when it's time to venture out to school and such. It does make sense to be cautious around others when you take your baby in for doctor appointments, especially to the CF clinic because that is where you know for sure there is a possiblity of contracting something that could really effect the child, but other than that, you are going to do your baby a disservice by sheltering them. And of course it is natural to have dobuts and be scared for your child, but it is something that you really need to work through and there are pleanty of people on this site that can help you out with that!
My husband was diagnosed with CF in 82, back then they knew virtually nothing about the disease, what caused it, how to treat it...and his mom didn't have the option of staying home with him-she was a single mom with two boys so everywhere she went, he went. Now, you will hear a lot on this site that everyone's CF is different and that is SO true. There is no way to determine who will be effected in the lungs, digestive system, reproductive area (for males) until they reach that point in life where you notice they are effected in that area. But my husband swears up and down that his mom taking him out, taking him to friends houses, and having a big brother who brought colds home from school and such (so he got it second hand) probably made it better for him when he started preeschool at 3. He had some hospitalizations when he was younger, and his CF is in his lungs, digestive system and reproductive system, but for the most part he has been lucky and been healthy. Can we contribute that to what his mom did and didn't do with him when he was younger? Nobody really knows, but he does think that early exposure to friends, family, his sibling, play dates, preeschool and such made his transition into the "real" world better for his health.
Best of luck,
Julie (wife to mark 24 w/CF)