Hi Dave,
The use of variety in your instructional delivery is important just as you have outlined. The mini-lecture format and then a discussion, Q&A session, etc. gives the students a mental break and helps to keep them engaged.
As for breaks this all depends on the flow of the class. I like several shorter breaks myself though I don't make a big deal of how and when the breaks will occur because once I do the students start to watch the clock as we get closer to the announced break time. This means I lose valuable class time as… >>>