Dress Help!

Not for me, but for my 11 year old daughter... we have a christening to attend in 2 weeks. She is the Godmother - I'd love to get her something nice, cute, and age appropriate. I have a couple of things working against me here, 1. She is a very tall 11 year old, as in 5'4" tall - she would wear a 16/18 in a dress just to get the length right, so this rules out a lot shops. 2. It is an iffy time of year - certainly too late for a sundress, but it could also be too hot for something too warm. 3. Talbots Kids has closed. They were my "go to" and now they are gone and I am up a creek. The only thing working for me is that she still likes what I like, so whatever I pick will probably be well received. I am in full panic mode now - any suggestions????? xoxoxoxo, Brie