Just saw this on Kickstarter: TOB Cable: One cable for everything

Based on personal experience of backing multiple projects on Kickstarter & Indiegogo, both have options to send out a questionnaire to backers. You are probably best off using this to send a questionnaire out prior to starting the assembly process of the finished product (or possibly ordering materials) to determine who wants a camera, and to choose which options.
I would allow 2 weeks minimum for responses, and even then you can still expect up to 10% of non-response, so you are best off using a queue order system, and grab the first X questionnaire responders off the queue and use them for the current batch of cameras to assembly and send out.