Your student’s age demo is a key lecture/seminar ingredient. This is what I would advise…
25-30 yos are ready to hit the ground running and have put behind them all of the teenage immaturities. If it is a short course as you say, they need to know what the market was 5 years ago, today and where the market for design will be going in the next 5 years based on evidence. ( you have some homework to do here).
What they learn in your course should allow them to interact with other professionals on a day to day basis. (i.e.strategy planning, trends, global issues, design management, Design Thinking and big picture issues).
I find it useful to split the course in half and teach module one to introduce material that then build upon it in the second half of the course. This illustrates to students how to apply design in a problem identification/solving environment.
Very important to set expectations on the first day. Tell them what they will be learning each class and what the outcome will be at the end of the course.
If this kind of information piques their interest further after the course, then they can choose to go deeper into other more traditional classes that teach more ‘hands on’ skills, history of design and contemporary design process methods.
Good luck…
P.S. - If you can design a social media component that allows information to be shared outside of class then you will capture more of their interest and attention.