My mother died a couple of weeks before the entire family was off to France for our dd's wedding. She was in her late 90s, though, and had been suffering from dementia for ages, so TBH we were all somewhat relieved that it had happened then, and not while we were all away - it would have been awful if none of us could have been with her, not that she seemed at all aware of whether we were or not.
Her death did not cloud the wedding at all - nobody could really be too sad that she'd finally been released from a horrible disease. Obviously these weren't necessarily common circumstances, but I honestly don't think we could have cancelled anyway - it was quite a big do so never mind caterers, etc., a lot of people had booked flights and accommodation, etc. And I'm sure she'd have been the last person to want such an event cancelled on her account. We did of course think of her a lot, and drink various toasts to dear absent Granny.
What would the bride's grandfather say, I wonder, if he could? Most grandfathers would, I'm sure, want it to go ahead, and for the family to think of him, and maybe raise a glass of bubbly to him.