IRL issues, complaints, comments, and shops are much more important than online issues, complaints, comments, and shops... I don't think you need to apologize... All you need to do is, every once in a while, if you haven't done anything with the sprites, just say "Haiz! Imma not dun yet, I haz the IRL stuffies goin' on" and I will completely understand, and, for that matter, everyone else should understand too.
However, if they don't, we can tell that they are just children with no responsibilities or whathaveyou and therefore have no concept of how hard time is to manage...