Multi-sizing Flower Girl Dresses?

We are having all our nieces and nephews walk down the aisle together all as Flower Girls and Ring Bearers. However, we only have two flower girls age 3 and age 11. Naturally I want the 3 year old in the most adorable fluffy dress I can find because she’ll love it, and I’ve asked the 11 year old what kind she wants and she’s said “kind of poofy.” She’s a young 11 spirit wise but also a big 11 body wise(probably 5’3, her dad is 6’4 🤦🏻‍♀️)
So I’m having a hard time finding dresses that look cohesive with each other, allow the 11 year old to have some poofy-ness, but also somehow allows her to look a little more mature? And one that will actually fit her too lol I guess my question is, has anyone had any luck finding dresses like this (that aren’t $70/dress) or is my only choice to make them tulle skirts and find a matching bodysuit for them?
I would like them to be dusty rose and the theme is pretty rustic!
Thanks in advance!