I think funerals have changed recently. I have been to ones where the family have asked not to wear black, esoecially when the deceased have been young, so it shows more of a celebration of life. Out of brown or grey I would go with grey. You can always pick up a mega cheap black suit from asda, primark or matalan(I know, but if its not going to be worn often should be fine), if you are gonna feel very self concious about it. I would think its fine.
Hope you arent feeling to down and try and keep your chin up xx