Actually I'm mother of the groom, does that make a difference?
I struggle with wedding outfits full stop TBH. It always seems to me guests are almost in fancy dress, dressed up as wedding guests rather than themselves. I prefer a summer dress or a suit that I'll wear for other occasions and is more "me".
At all the weddings I've been to recently (I mean in the last 10 years!) the mothers seem to have some sort of dress and coat combo that is very obviously a mother of the bride outfit, probably with shoes from the same fabric.
Can I wear something more "ordinary" without offending the bride and her mother?
It would be something good, I'd spend equivalent money, but on something I actually like.