Áine
You will have a whale of a time!
I run a whistle club at a local school for 6 - 10 year olds. I do teach them to follow a tune from the music but I find the easiest and quickest way is for me to play a low D. This way they can see clearly what I'm doing and we learn a phrase at a time and then link it together. As soon as possible I stop playing although I may mime just so the newer ones can still copy if they wish.
Have fun
Baz