Two occasions in September, I wonder if a dress exists that could cover both.
First is a work party, it won't be formal or really have a dress code, but I suspect a lot of women will probably wear dresses with trainers or sandals.
Second is a wedding - church ceremony and then reception in a local sports facility - I guess fairly standard wedding vibes.
I wouldn't want to be overdressed at the work party, and would want to wear trainers there, so maybe it's a big ask....but maybe a fairly simple dress could work for the wedding if it was the right one? I'd much prefer natural fibres. I'm size 10-12 and mid 40s.