I have always left my daughter home for the CF walks. I was nervous about cross-contamination, but I was also not interested in pushing a stroller the whole walk. We had t-shirts made up for our team with a picture of my daughter on it. That way, we felt that she was still with us and our purpose was on our sleeves, not just our hearts : )
Our walk is a pretty long one and has a lot of hills, so stroller pushing isn't much fun. But check your route, you may want to bring your baby. As they get older and have a sense of how to manage infection control, I will definitely bring my daughter -- I think its important for her to be a part of the fundraising and learn to give a little back.