It would be fine for a funeral.
I do think it needs subtle accessorising, though, to bring out the smartness.
If you were to wear it another time for a reception, maybe with strappy silver sandals/thin silver belt to accentuate your waist (which is very definitely something I don't have, but you do)?
For this day, the belt would work and maybe if you have dark plum/maroon coloured shoes (wedge heels are comfortable when you're feeling wobbly, at it can be a long walk from the car park if you aren't in one of the directors' cars), they could be worn? It's not the same as wearing scarlet, after all, if you're worried about that.
There's a good chance that whatever you pick, you will change your mind on the morning, so it's still good to have more than one outfit ready (don't forget to get a couple of packs of M&S tights in advance if you wear the things, just in case).
I don't suppose you've thought about your hair yet - that jumpsuit would look incredibly elegant with your hair up in a chignon/pleat for this time, for a wedding, I think that having it looser and tumbling would look great - I'm guessing that you have lovely, dark hair, going by what looks like a great tan.
By the way, being a nosy person, it looks like your bedroom is lovely, calm, crisp and cool - I love old fashioned bedsteads! So you've obviously got great taste when you feel able to let yourself decide - try and be confident that you will look the best you can.