I'm not really a fan of the whole 'Turn up to your own wedding driving some sort of awesome car that doesnt really belong to you and probably never will'. It just seems so ridiculously fake. Effectively all you are really doing is getting a taxi - a drive to the wedding. With that in mind, I think something like a silver S Class Mercedes would do the job just fine. Few of my or her circle of friends are really that into cars anyway so it doesnt even need to be an S55 AMG.
Turning up in somebody elses rented Supercar just seems so crass.