I will be about 20 weeks pregnant. I have bought this dress
And I have black heels which I can walk in. The wedding is (secret) registry office in about a month, so it could be a little chilly. But obviously isn't in the slightest bit traditional, or posh. Only the 3 of us will be there, me, DF and DD 
My question is, oh stylish Mners, what kind of cardigan should I get? Crew-neck? What length? And I am not afraid of colour (I like jewel-like shades, nothing wishy-washy), but obviously my shoes will be black. Does that matter? Help...