I would wear a blouse or shell that added some color and brightness. No cleavage, and probably not a shimmery or sparkly fabric, but a flattering color that would pop against the black.
Sorry for your loss.
Last year at this time I did the eulogy at my dear aunt's funeral. I wore a business suit, knee length navy pencil skirt, duster length matching suit coat (with no lapels ... not a menswear type of girl), navy tights and pumps and a lime green jewel necked knit shell. I also wore a string of hand made beads in navy, green and yellow to give a false V-neck impression over the shell. For most of the event I wore the jacket done up, with just a bit of color showing at the neckline, but opened the jacket buttons when visiting with family at the tea after the funeral.
This is my go-to outfit for when I want to feel calm, competent, and professional. It works for public speaking engagements, job interviews, important meetings and also is appropriate for funerals depending on what blouse, shoes and accessories I wear with it.