I have a passion for both engineering and teaching. I've found when I only teach full-time I miss engineering, and when I only work as an engineer full-time I miss teaching, so I do both. I work full-time as an I&C engineer and teach at night one class per term since that gets me the best salary. The teaching money is a drop in the bucket, so I tell everyone that I work as an engineer to support my teaching habit.
I've taught a variety of courses, including theory-based controls course at one local university and applied controls (with PLCs) and instrumentation courses at another. I've had my current teaching position since January 2007.
The main problem with trying to teach is the one you've already identified - unpredictable travel schedules. I've been fortunate since I am assigned to a project at a local work site, so I haven't had to travel out of town and I'm able to commit to teaching. I currently don't have that problem, but my project is ending soon and I may have to risk it in the future. I just keep my management at both school and work completely informed of what is going on at each place.
Management at my engineering job likes the fact that I teach, so they've tried to keep me on projects where travel is minimal. I've recruited several top students for entry-level jobs and internships, I've used lectures I've developed for department training, and I keep all of my theory skills sharp so people ask me for help on tough projects that require application of control theory above and beyond the normal stuff used day-to-day. They allow me flexible working hours so I can leave a bit early on the days I teach and make it up on other days.
Management at my school likes the fact that I can teach my students more than the typical theory in the textbooks and have them developing practical knowledge as well (e.g., using industry codes and standards, producing construction work packages with typical documentation, etc.).
The students like it because I can mix the theory with the practice in a way that they learn fundamental principles and how to do the job in the real world.
I like it because I can be bored at times as an engineer doing the same type of thing repeatedly, but the teaching reenergizes me.
It's win-win-win-win, at least so far.
It is a lot of work, though. With the exception of the course description and course objectives (which were written when the curriculum was formed), I do all the work to create a course. I write all of my own course materials, do my own textbook selection (and reevaluate regularly), grade all of the homework, quizzes, exams, and labs, give the lectures and supervise the labs, etc. It's a lot of work - especially the first time I develop a course. Unfortunately for me, I teach in a program that just started a few years ago, so I haven't taught the same course twice since I started. That means while I teach one course I've been developing the next. I've created and taught six courses since I began teaching in that program. I haven't slept much, that's for sure. I am getting a little burned out, but I've decided I'm not teaching this summer. I need a break. I'll be back at it in the fall, however.
I'd tell your wife that the chance of you getting to know a female student well enough to get into trouble is pretty slim in a technical curriculum like the one you described. First of all, the student population in your program will be predominantly male. Besides, everyone who teaches knows teacher-student relationships can be very dangerous for the teacher (e.g., sexual harassment charges, not to mention getting fired and/or sued). I won't even be alone in a room with a female student. I've had only a couple of hot young women in my classes over the last five years since I've been doing this. You might see some in the hallways or other places on campus, though. I know I do.
Best of luck in your teaching endeavors,
rytko