Skills: Escape Artist 4, Hide 4, Knowledge (nature) 4, Listen 2, Move Silently 4, Perform (sing) 4, Sense Motive 4, Spot 2
Feat: Either Dodge, Agile, or Skill Focus (Perform [sing])
For Faerie Formation, I wouldn't increase Strength. Most swarms have a Strength of 1. Instead, I'd give them a morale bonus of +5 on attack rolls (borrowed from the Swarmfighting feat in Complete Warrior) and a +5 competence bonus to AC. Maybe also state that they cannot be flanked (since they've "got each others' backs")?