Suggestions on girl's dresses

I'm having my nieces and nephews as my wedding party. My older neice is a size 12 and younger neice is a size 6.

I've been to Kohl's, they didn't have anything appropriately formal enough. I went to Estelle's Dressy Dresses yesterday and they had cute dresses but only in size 4 and 16! The lady said they couldn't order them.

I just went to Macy's website and Limited Too and didn't find anything appropriate either.

I'm looking for matching lightweight dresses, not satin or with lots of crenalin on it. I'd like to find something in pastel pink or lavender but will also go for pastel blue or mint green.

Have any store suggestions local to eastern Nassau? My sister will be paying for them but is ok with me picking them out.

I'm trying to avoid going to David's or something like it to pay over $100. for the dresses.

Any suggestions would be appreciated!

Have you tried Sears or Century 21? I was there about 3 weeks ago, and saw some Easter dresses that would work; but I'm not sure what they have in stock now...

Thanks for the suggestions. They don't have a lot listed on their sites so I guess I'm taking a trip to both.

Any other suggestions?