Fairy Tale sizing help? Skip the darts?

Me again. My daughter's dress turned out so well that I offered to make matching dresses for my nieces (who are also flower girls in my brother's wedding). The catch: They both live two provinces away and there is no time to send a muslin back for fitting. One of my nieces' measurements are: 28" for waist & chest Should I make her a size 12 and skip the darts? Will that give enough room in the waist? The other niece: 24 1/2" chest 23" waist Should I make size 7 even though it might be a bit roomy in the chest or make size 6 and skip the darts? I'm not concerned about the hip measurement because I've basically turned skirt into peplum and using tulle. Pic of my daughter's dress to show as example: Or is this all too risky and I should go with plan B - buy the girls matching bodysuits and make three LTTS tutus?