So, my first thought is, "don't do this." I mean, the history of computing is a specialized topic. People get PhDs in it. Your having taught computer science in no way qualifies you do do it, anymore than a historian could turn around and teaching Fundamentals of Data Structures (to pick a random intro-level CS class) just because they too use "data" in their research. It's fundamentally disrespectful of the fact that this is a specialized field to have non-specialists teach it. It'd be like me getting assigned to teach a class in quantum physics just because I sometimes teach on the history of physics. It'd be a bad scene.

But I know that's not very helpful at this point, and I know that CS departments are not always aware that there are professional historians of this (or have the resources to hire them, etc.), so I would strongly recommend that you look around a bit in the academic history of computing so you have a sense of what the actual historical discussions are, what the kinds of questions historians ask are, and how to avoid teaching bad history, which is to say, probably much of the history you have read in popular books and articles on the topic (because most popular books and articles are bad history by default, but anything that touches on technology, silicon valley, etc., seems to be particularly awful).

The Special Interest Group for Computing, Information and Society (SIGCIS) maintains a resources page that includes, towards the end, a section on "Key Books and Articles on the History of Computing," which is heavily annotated. Note that some are labeled "start here" as being considered fairly fundamental. SIGCIS is one of the main professional societies dedicated to serious study of computing history.

They also have a syllabus repository, which includes many donated syllabi from top scholars in the field. Perusing them you will find there are many ways to teach such a class (chronological, thematic, etc.).

Lastly, as just a personal recommendation: since you are not an expert in this, and are not going to become one in a few months' time, I would take an attitude of, "let's learn about this together." Pick a few of the books and read your way through them with the students. Don't lecture them — you don't have the mastery for that. But you do know about computers, and you have been around the world a bit more than they have, and you likely have a good head on your shoulders. "Let's read books and talk about what we think about them" is a perfectly good approach to an undergraduate class.

I am not a historian of computing (though I am a historian of science, and have read around this history a bit), and if I were teaching such a class, that's how I'd be doing it. The one book I'd for sure have on my syllabi would be Paul Edwards' The Closed World, both because it is a very interesting history of computing in the Cold War (and a good Cold War history at that), but also because it engages in making a "big argument" about the role of computing both as a practice and as a discourse in the politics of the period. It also includes a chapter on both Terminator and Terminator 2 which could make your life easier if you had them watch those, also. :-)

Tracy Kidder's The Soul of a New Machine is totally readable and builds up a non-Silicon Valley view of microcomputing (and will be revelatory to younger programmers; one of the characters in the book writes the kernel of an operating system longhand on a pad of legal paper!). Just to name another one that I think would work well with undergrads.