Cover-ups for bridesmaids - what to choose?

I would love some advice! I'm about 1 month and 5 days out from my wedding. We will be getting married on Vancouver Island in late September. We've been planning the wedding for so long now, and I must have been soaking in the summer sun, because my colours are much more in line with summer than a fall wedding. The men will be in cream linen pants and vests, and the women will be in pale shades of chiffon - pale brown, pale blue, pale pink - very dusty, neutral colours. I was thinking all white and green bouquet and floral arrangements. I live in central/ Northern BC, and now that the weather is starting to turn cool and damp I'm wondering if I should toss in a dark plum colour to the floral arrangements, and try to find some sort of shrug to provide for my bridesmaids and myself in case it is cool. I want people to be comfortable. I could go with like a neutral, cream or plum coloured pashmina or bolero, but I'm really adrift on this decision! Since each dress is a different style/ colour, I'm not sure what would look good all together. Am I stressing out over nothing? Or should I just make a decision and run with it?