Do not sacrifice practice exercises for more content. We learn best by doing, not by listening and we learn more through repetition and concept integration, than through isolated topics. Thou shall ask and show how the training can be applied to the learners' job needs. Software functions taught outside of a job context are meaningless to most learners. Thou shall honor the time schedule and start class on time after breaks.
Time is money in a training class.
If you start the class late, you are wasting the learners' time and setting a precedent for others that schedules are not important. Stick to any time schedule you announce. Take short mini-breaks to increase retention. Thou shall have fun and enjoy the training. Learning should be fun for you and the learners.