I'm going to go against the grain of the other two answers here... It seems entirely viable to me.
For weekend courses you'd possibly do well targeting local business owners, though perhaps one day would work better than both - but I don't know. Small business people frequently don't have any time to be doing courses in the working week. You then make a feature of respecting their overworked week in the marketing!
You could perhaps offer a taster to security issues, help them to understand staff security risks, business security risks and the like, they will pay very well if they feel the need is there. The scare factor of the security risks posed by their staff actions could be the marketing key there.
There's also a possible market in self employed freelancers and contractors, but I suspect they'd be far harder to sell to.
If you target each course at a particular market (lawyers, accountants, media businesses, advertising agencies, etc) you may find take-up is higher as you can pitch the course as being targeted at that particular sector. For example there may be legislative issues that mean lawyers have to take security that bit more seriously, and your marketing can reflect that. Small business owners are also the people who probably have the lowest awareness of such issues, yet could be hurt the most (business closure) by a serious failure.
Thinking laterally a little, if you're weak on sales, marketing and the like, could you not have a chat with one of the professors / tutors in the business faculty? Perhaps you could get some help, pointers, or perhaps try the first one or two as a joint venture. I hesitate to mention it, but maybe even a student in that area could freelance some marketing materials for you.
You may find your local chamber of commerce would be interested in evening or weekend courses for their small business members, and it would be of benefit to you being affiliated through them. This would depend on what training they already provide of course.
A basic website to get more information, some flyers and targeted materials and you could easily find a niche here. Some worthwhile handouts and check-lists for them to take away, and some follow up resources on the website perhaps. Don't forget a decent end of course questionnaire to ensure you're meeting the need, and to identify possible follow up courses.
Don't let not being well known put you off either - 30 years experience is ample, and university professor is excellent credentials - after all so many commercial training courses use a 25yo lecturer with little experience of the field, and less than 6 months actual experience outside of delivering courses. You have a selling point, and should try using it.
There's going to be quite a bit of work putting the first couple together, but once you have the materials, and the shape of the course settled the overhead is marginal, aside from periodic updating of sections to ensure it remains topical and timely.
Possibly a naive question to close, as I don't know contracts or limitations in US universities, but does your own time of evenings and weekends count as pursuing outside opportunities? Superficially it seems the overhead of preparing materials etc needn't count, but obviously the courses will.
