I see nothing wrong in your selection. The widow has made a request and it�s appropriate to honour her request. Interestingly, there�s always the veiled line of social acceptability. I celebrated a funeral last month where the family requested that those attending dress for �celebrating her husband�s life and not mourning.�
The service was at our local crematory. Everyone was dressed as I would have imagined; nothing dark, generally what one might describe as professional office attire�except for one couple. The young man had on jeans and a bright orange t-shirt that had an advert for B&Q on the back. His partner, who somewhat resembled a saveloy with a string tied in the middle, wore a half-length white t-shirt. Emblazoned in large pink letters, trimmed with a diamante Motif was the word �sexy,�
It just lead me to ponder on what they might have worn to a �casual� occasion.
Your choice is fine and I know your friend will be grateful for your attendance.
Be well
Fr Bill