I feel your pain, am off to a wedding on Thursday.
I'm having same dilemma as you and after trying everything on in my wardrobe about 55 times this weekend am going for flesh coloured tights with nude heels and picked up some hold your gut in flesh coloured tights at M&S today.
Purple mac and clutch sound good - splash of colour with lbd
Have you got some earrings and maybe a scarf that would tie it all together? Do wear tights if only to keep warm, shivering is not a good or trendy look. Add layers to help keep warm, waiting for photos can take ages. Have a lovely time!