Thanks for those responses.
I wrote an email to the revenue and a reply arrived this morning...fast response. We would need to be a registered charity to receive the 'tax back' and yes, that would go straight to the fund to help victims, not back to the donors.
However it looks difficult to get recognised charity status for tax purposes. We may have to forget that possibility.
Tommy, thanks for the comments on the personal tax issues around donations. I've sent another email to Revenue to clarify things on that score. Our friend in Sri Lanka says not to worry about tax issues at his end, he has it sorted. Don't know how, but he understands the issues for himself and is happy to run with it.
I'll let you know how this pans out.