There are some great comments here. I don't need to repeat what's been said, but would like to add that you should not go for a big launch yet. Instead, invite some people who fit the definition of your core audience and ask them to test the site out. Use services like uservoice.com and survey.io to collect user feedback and make sure your product has a solid market fit. Doing this will make sure you don't miss the mark at launch, while at the same time providing some key insight for messaging to be used with a more prominent launch. Good luck!