This is my first time teaching mathematics. I've been giving lessons based on a certain textbook which contains excellent exercises (not just the exercises, but the order in which they appear leads one to discover mathematics for yourself). However, the textbook has a solutions manual, and I am certain that if the source was revealed, then students would purchase the manual and defeat the purpose of the course. I am wondering if it is ethically acceptable to retype myself some of the exercises and exposition from parts of the book in order to obscure the source (and perhaps reveal it at the end of the course)?
My intentions are solely to create a joyful mathematical experience for the students. There is no intention of plagiarism. My only worry is that the exposition is so good that I don't see how much I can deviate.
Clarification: The course is not intended to have students master a technical subject and then solve problems under a time pressure. This is not a mathematics course for engineers or scientists. Rather, problem sheets are given each week, with the requirement that at the end of the week the student turns in 10 solutions to their favorite problems. The focus is on quality of writing and clarity of though. In fact this entire issue is now resolved as I have communicated with the author.