Quick disclaimer: I worked as a corporate trainer in technical environments for around 4 years, so this is probably more information than you need. I hope it's all helpful.
How you structure your class ultimately depends on what information you're trying to get across, but a good place to start is a general UX process that you'd like to use, even if you don't currently follow the process in all situations. If you're not quite sure what a typical baseline UX process might be, I outline what I use on this post. Your process may differ, but it's a good starting point, at least.
Real world practice sessions and examples are helpful as well, especially as your group gains knowledge and experience. A great way to introduce people to the concept of user experience is to give examples of UX, and to explain why those experiences are bad. Many times, real-world examples hold more power than online examples.
For instance, you could use this elevator control panel to show the idea of usability patterns and the perils of violating an established pattern. Traditionally, elevator manufacturers organize their floor number listings in columns, with the lowest floor appearing in the top left column, proceeding to the highest floor. This control panel has the lowest floor on the bottom left, and uses an ascending row and column structure, moving from right to left and bottom to top. While in many ways this may make sense and indeed may be a more logical pattern, this panel violates an established pattern and norm, making for a very frustrating user experience for the casual user.
Another example you might use to establish the importance of proper labeling and using familiar controls for their intended purposes could be this confusingly-labeled door handle. Imagine you walk up to this door and see this setup-- you are instantly forced to either assume that some idiot has used the wrong label, or that the control in-place is at best a make-shift fix or downright deceitful. Whatever your decision, your overall confidence in that particular door and perhaps the owners of the building as a whole is going to plummet as a result of a relatively small user experience faux pas.
As your sessions progress and users get more used to UX concepts and errors, giving them real-world UX problems to resolve becomes even more appropriate. I strongly recommend coming up with a handful of scenarios that are either analogous to ones you've recently tackled, but that your group may not have intimate knowledge of. Have one person lead a whiteboarding session for the group, where the problem is discussed. Walk through the entirety of the problem as you would were it one you were facing within your company. Define business needs, provide any relevant statistics, data, or feedback, and create a mockup from scratch.
Whatever path you decide to take, it's important to remember that your role in practical exercises is as a facilitator. As a subject matter expert, the temptation will always be to jump in and correct errors as they are made. It's important that you let the group come to their own conclusions as examples, and only address potential issues in either a post-mortem, or, if things are straying VERY far from the point, to re-focus the group on the goal gently.
A couple of things to remember:
Whatever training materials you use, your age group is likely going to have a mix of people that will want either digital or printed copies of the materials. Unless completely impractical, be prepared to present the material to each user as they request.
Facilitate discussion, especially in groups that may not know each other well or feel comfortable around each other. Starting each session off with a quick icebreaker game or question is a great way to get everyone feeling more comfortable with each other. I would always ask everyone to introduce themselves, giving their name, their position or department, and one thing that people at work may not know about them. I'll usually go first saying something like "I'm Doug, and I'm the company's UX Engineer. Something most people here don't know about me is that I have a twin brother. We're not identical-- thank goodness, I wouldn't want to be that ugly." it gets a chuckle and sets a more relaxed tone, and helps to open up people a bit, both to each other and the class as a whole.
If you don't know the answer to a question, admit as much. Faking your way through an answer, BS'ing, or half-assing a response is the easiest way to quickly lose credibility in front of your class. If you can quickly and easily find the information, take a moment to look it up. If not, promise to get the answer to the question, write down the question and the information about who asked it, and send the answer to that question to the group, not just that individual.
I hope this helps! Let me know if you have any questions.
I'm also curious to hear what other suggestion others might have!