If you are using these lessons in a class, then all the students should use the same keyed harmonica. I usually have them use the key of C because most of the cheaper harmonicas only come in the key of C. (You have my permission to make copies of these lessons to distribute to a class or your friends.)
So What If You Don't Know The Songs?
Only attempt to play familiar tunes. If you can hum it or whistle it, then you can learn to play it fairly soon. In fact, think of yourself as singing the song through your instrument and the reeds of your instrument as a substitute for your vocal chords.
You will soon discover that you do not need the harp tab numbers. You brain will have imprinted upon itself where the holes are and whether you blow or draw. It will be much like whistling. You will just know automatically where the next note is on your harmonica.
Happy Trails To You
I Dream Of Jeanie