I'm going to give you a very different answer than most people: Don't try to emphasize the differences. Do you have a deep enough understanding of these three fields to fully outline the differences and similaries? Do you understand the job market and job perspectives post-graduation? Do you know what is common across multiple universities? Probably not, so don't try to.
When I was an upperclassman at my university, I would routinely participate in open houses, where I (and other software engineering students along with faculty and staff of the department) would stand in front of a room full of perspective (or in some cases, accepted) students who were trying to figure out which university they should attend, or which major they should start in. Dealing with questions about the differences between computer science, software engineering, information technology, and computer engineering was commonplace.
Every time I was asked about this topic, I emphasized what courses were part of the software engineering program, what the university's software engineering curriculum offered, how you could tailor the curriculum to emphasize different aspects that would be useful in various careers, my experiences on the co-ops that I had completed and internships that I had, some of the opportunities that my friends and colleagues had, and so on. When I talked about what other programs offered at the university, I did so in generalities, giving the extremely high level differences between the typical skills of a graduate in each of these programs.
Trying to explain the nuances is extremely hard when you are only talking about one university and have access to all of the information and guides from each of the departments and know people studying all of them and what they are learning in their courses, such was my case. However, in your case, you will be talking to people who are each looking at different schools, colleges, and universities. So not only will you be talking in generalities across academic disciplines, but also across universities. You are more likely to say something that would give the wrong impression or lead people down the wrong path - exactly what you are trying to avoid.
Rather than focusing on the differences between academic disciplines, talk about the career using your personal experiences. Talk about the jobs you've had, the things that you have done, what your typical day or week is like. Talk about things that you know well and know specifics about. If you want to talk about your education, make it about your education - mention the university you went to (and when you went there, as things change over time), the courses you took, the things you learned, and so on. Just don't generalize it into things that you don't know.
