It is a hard, and saddening situation. Without knowing you personally, or your way of coping, I do not think anyone can give you what you need.
Funerals themselves are a way of saying goodbye, honouring the person for what they did in life, and reliving past memories etc.
The funeral, the crying, and the laughter and happinees from reliving memories are all necessary to the grieving process in my opinion.
You could come up with something on your own, rituals need not be complicated, say goodbye in the way which feels right to you.
I am truly sorry for your grandfathers ill health and do hope you find a way to cope with the situation you are currently in.