We've always had real Christmas trees. Our son, now 4, was diagnosed at age 3. He's never had any problem with the tree. He also does not struggle with allergies or asthma. Last year, our first year of knowing about his CF, we still went forward with the real tree and are getting another real tree this year. I think it just depends on your individual child's situation. If he/she has a lot of problems with asthma or allergies, you might want to avoid the real deal.
Jena