Hey Sonia.
First of all lemme start off by saying u r a really sweet daughter.
Secondly, I know of 2 families (both in pak n in both cases the mother has/had cancer).
I'll tellu wat they did and i think there have been no talks about it.
First family had a grand affair invited 1000 people to the wedding and this way mother met every1 at the wedding. She had cancer and is no more.
Second family 's daughter wedding is in a week and as far as i know they r going to have a weding in a masjid as they have done it with all their kids. The mother has cancer and is at her last stage.
Above examples were just to let u knwo that it'd b aright if u go with either option n no1 wud talk. But i can understand ur pain of having a grand affair at a time when ur heart is crying. I would say talk to ur mom n tell her if she wants to see every1 at the wedding then u can invite every1 over but tell her u'd rather spend tiem with her taking care of her, catering to her needs rather than looking after the guests.