There are a lot of good suggestions here, my only exception is in teaching, tonguing. If you teach it. First show them how to make two G quarter notes using tonguing, then show them how to put a grace note between the G’s in place of tonguing. Let their ears hear the difference and chances are they will see that the grace note adds a more irish feel to the phrase. You can explain that the use of tonguing varies from player to player, but generally a lot less tonguing is used in Irish tunes than one might find in other genres or with other wind instruments. Its the use of ‘ornamentation’ that adds the unique irish whistle style to playing. You may want to demonstrate, playing a tune with every note tongued and then repeat it with every note ornamented to show them that neither extreme sounds right.
Also there is a related C&F topic: <a href=http://chiffboard.mati.ca/viewtopic.php?topic=6712&forum=1&28>Recommended Beginner Tunes which you can use to draw tune suggestions for your class.
Finally, if you teach one tune with notation (ABC or Standard) you might also want to teach one tune by ear alone. With the mixed background, you may find that learning to play by ear is something the less trained players pick up quicker, it may put them on a more even footing. It may also present a challenge for students that know how to read music and keep them engaged in the class.
All these ideas and techniques aside, there is one thing that will improve your teaching more than any other thing.
Let your students see and feel your passion for the music. Find a simple tune you really love and teach it to them; warm up your fingers playing a couple tunes before class that mean something to you. Learning music is more than how to put fingers on a tube and blow air through it. You are teaching them how to express things that can’t be put into words, play one of your tunes that demonstrates just that.
Music is more than hearing with the ear, its engaging the heart and soul of the player and listener, connecting them. Make the tunes personal, pick tunes that have a personal meaning for you the teacher. A personal meaning doesn’t have to be sober or serious; if the tune is just a fun, frivilous feeling, share that too. Maybe share both in the same tune, play the Minstrel Boy, the way you played it the evening of September 11th, lamenting the loss, then play it again like you needed to express your bravado while walking through the haunted wood.
For me, teaching music is all about showing others how you …