Easiest way to declare extra income?

Hi,
I am a paye worker ( school teacher). A few years ago I was self assessed through ROS for extra music tuition I did at home. I ceased doing it a few years ago (not worth hassle!)
I also play music in my local church. This isn't a paid position, although there is a fund to reimburse for any expenses. I do it as a favour/ out of good will.
However, recently I've been asked to play at funerals a few times. There is a set fee for this (in any church) and the undertakers have handed me a cheque each time. (Haven't lodged any yet as am unsure what to do)
I presume I need to declare this, and if so, what's the easiest way? There would generally be v few in the year, I might make 500 euro if I'm lucky (before expenses of traveling, photocopying, buying music, etc). Do I wait until the end of the tax year or do something now?
I am absolutely clueless in this. The income is v small and I certainly don't do it for the money,when you take out the expenses it's v little, so might not be worth the hassle of doing it at all! Thanks in advance.