I'm really not a fan of the jacket and for the occasion just think it would look like a little out of place.
The dress is nice but I don't think is anything special (as in you could find a floral occasion dress anywhere) and for me I can't see much point in buying it just to take so much length of it.
If you feel the need for a jacket then I'd probably just look for a dress with long sleeves instead and consider a colour that contrasts with the bridesmaids rather than matches - it'll look nicer in photographs and won't give the appearance you've tried to join the bridal party.
Yumi dress in various colours
Not suggesting this is perfect but I think it's a good example of something that doesn't need a jacket and works as a good complement in any colour really to the pink dresses (as it has that detail) but without matching.