I think they're very grown-up, but not frumpy. When I look at them, style-wise they remind me of dresses Kate Middleton would wear.
I don't think that, at 40, you would look older than your years (the silk tunic dresses and some of the lace panelled dresses are gorgeous) but you wont exactly be looking young, iyswim. Grown-up. Mature. A Mum, but certainly not Mumsy.
Sorry, can't help with Kaliko sizing.