The dress arrived and it's just perfect for this project. The material is a bit casual for a formal event, but hey it's Dayton. That's how we roll on the East Side.
I worked out the circuit--and I'm happy to report I can carry 10 LEDs on the two programmable pins on the Adafruit Gemma, using the 3.7v 500mAh Lipo battery. I'm going to bring an extra with me just in case I run out of juice through the event.
I'm placing the LED's under the front white stripe to soften the light. The stripe is on a panel that lifts up from the rest of the dress, so I'll use another piece of fabric to sew the LEDs onto, and then attach this piece to the stripe panel from underneath. I have it worked out in my head, but I'll also sketch it out to make sure I plan for the circuit to the mic and Gemma.
Next, I'll sketch out the dress and circuit design and start sewing the LEDs and Gemma in place.