Peer enthusiasm will then be able to sell the program for you. Technically easy music has worked better for me at first. Students don't mind playing this when they know they have to memorize it. I've been more successful using shorter selections in the beginning, as the task of memorization doesn't seem so overwhelming. Then, later on, I add a couple of medleys.
Harmonized music is fine as long as the parts are scored fairly close together.
Also, there is a large selection of music arranged specifically for strolling on the market today. Establish a set program and use it all year. Once it is learned, all you have to do is review it from time to time. Rehearsing the Music Approach teaching music the same as you would any other literature. Intonation, technique, tone, rhythm and musicianship are extremely important.