The first planning stage:

Monday 29th March - Sunday 4th April:
Sarah .................. Brainstorm / post sketches for costume
Musicians ........... Start working on Music ideas

Monday 5th April - Wednesday 7th April:
Everyone ............. Voting on final design
Musicians ............ Still working on music
Dancers ............... Send in Measurements by 8th April

Friday 9th April - Thursday 22nd April:
Sarah ................... Making of the costume
Musicians ............ working on music till Tuesday 20th April

Tuesday 20th April - Thursday 22nd April:
Everyone ............. Vote on Music

Friday 23rd April:
Dress ready for shipping

Let me know if i have missed anything or haven't allowed enough time for.