Thanks for your replies (so quickly, too!
) I was surprised to hear that about steroids but apparently it causes them to lose control and they forget where the litter tray is and/or they can't make it there on time. If anyone has had experience with steroids it would be helpful to hear about your experiences. I think one person on Cat Chat had said to avoid steroids as while it helps while they are on it, once they come off of it they get ten times worse.
I'm not sure about any cat hospices in her area - she's in the US in the midwest.
Since i posted I've found a few websites where people have detailed their experiences with their cats and cancer and the whole treatment process does sound awful (hence more tears) - where as just letting him be and let him enjoy the last few months seems kinder in some respects. I guess I keep thinking it would be great if he could be treated and still have several more years of life. I do know my mom very well of course and I know she is watching his every move and is worried sick so despite how difficult it is especially from so far away for me to say let him go I know deep down it probably is best.
Will see what happens when she takes him to the second vet hopefully tomorrow - just dread her putting her down without telling me first.
Anyhow, will keep checking here for anyone else's experiences. Thanks.