Flower Girls dresses

I'm getting married in August 01 and was wondering when I should begin to order the flower girl dresses. I saw some I liked at David's Bridal and they say it would take 6 weeks to order a dress if they don't have the size available. My concern is if we order them too early the girls will out grow the dress by the time of the wedding. Any ideas?

We're using My Girl by the Temptations

Try this: (you can even hear clips of the songs):

I already had our flowergirl's dress ordered for our late Sep. 2001 wedding. I was also worried about growth. My sister-in-law took her measurements (they lives in Georgia), and she kept the tape measure somewhat loose, rather than pulling it snug, plus my niece was wearing a sweatshirt for extra padding. In the end, it didn't matter. The hollow(?) measurement, from the base of her neck to the floor was really all that mattered. She was measuring a padded 33, and the smallest size (4) was 37. The other measurements were all right in line with what she needed. We were also reassured by the shop that the dress makers put extra material in the seam and they had never experienced any problems. (I hope we're not the first!!) :)

We needed to order our dresses immediately because our dress we chose for the girls was being discontinued and the flowergirl was going to have the same dress. Prior to ordering, we were told to allow 4-6 months.