Helo masoka and so soryy about your mum.  I have been involved with caring for patients with terminal lung cancer and it can vary a lot from person to person.  I don't think you can be certain of when your beloved mum may pass away - is it possible for you to have a small bedside ceremony just for family before the big day?  I know it is easy for me to say this and only you can make a decision about it.  Whatever you decide, be assured that your mum would want - above all - you to enjoy your big day.  I think we all feel very alone when losing a beloved parent.  It is a very individual experience for everyone and sadly a very painful one.  Best wishes to you.  Annie