In general, I believe calculator use should be held until the student has pretty much mastered the reasoning behind conversion to and from, numbers in scientific notation. It is very important for students to learn to use the calculator to work with scientific notation (as long as it helps and does not hinder conceptual acquisition).
In this lesson, students were quickly introduced to calculators in the New Info section. Yet, we must make good judgement as to when to allow their use and when to ask students to use pencil and paper. During this stage, I would stay away from numbers that are extremely large or small, to avoid the painful writing of so many zeros. Mistakes are so easily made in these cases. This is much harder even, for students with writing difficulties. Once beyond the mastery of the underlying concepts, and using scientific notation in application problems, calculators will help for accuracy, speed, and as an accomodation tool for students with special needs.