I have sons who will (hopefully!) be graduating over the next couple of years and I would have got it badly wrong, thinking it was their day and my duty was to turn up in much the same way as I did for their end of year assemblies in primary school 
Two, senior, sensible, professional, not particularly image conscious women at work have sons graduating this year and the talk has been all dresses/bags/shoes for weeks. Their chosen outfits (I have been subjected to constant photos of the various possibilities) look like mother of the bride outfits to me. Is this normal?