While this is a lovely sentiment, the problem in America is not turnout amongst startup employees. Startups will not change the world giving their highly paid thought workers, who presumably already have unlimited vacation, free lunches, on site dry cleaning, etc, etc the day off.
Solving this problem will require an act (or several) of Congress. We need a movement to make Election Day a national holiday. We need early voting, and protections against voter disenfranchisement at the polls such as ID laws intended to target the poor, for whom the time cost of voting is already high.
Further, we need that to be a broad-based movement, not focused on tech people and tech issues. To the extent that could begin with businesses, startups could focus on innovative ways to reach out and help businesses who employ hourly workers, minimum wage workers, etc. Find ways to help these businesses get involved and get their employees to the polls. Give them free product, help them think through innovative scheduling options tied to customer-facing promotions, etc.
It costs your startup nothing to tell your employees to “take the day off” (aka WFH) Election Day. Businesses that employ those for whom voting costs hard money will struggle to join your movement, presuming you ever invite them. Innovate on that.
It’s great that you woke up in July, realized there was an issue here, and got informed enough about the problem to get some PR out of it, but don’t confuse this with making an impact.