The finest song about Aberfan that I have heard is by Greg Hastings who lives in Perth West Australia.I will admit to crying when he sang it at Fairbridge Festival, for me it was something very special as two weeks after Aberfan I was teaching in a school that was hit by a whirlwind and we were digging children out until the Fire Brigade arrived ,the best part of 30 mins.
You could always try Greg for the words