I will put one caveat on what Jaeger said: You might not be ready for that degree of playtesting. If your three buddies already have some experience with the system (e.g. playing while you run it), then when they run it, that's not a blind playtest. On the other hand, a blind playtest is an incredible amount of work, that you don't want to engage prematurely.
So you might think about doing a playtest first with your 3 buddy groups that is kind of a dry run for later, blind playtest. Yeah, have an adventure. Try to stay somewhat removed (e.g. don't be a player in the game). If they are not bothered by it, maybe observe play--without saying anything during the sessions about the game. This breaks several blind playtest rules. On the other hand, let's say you do that kind of testing and you find things that are clearly not right yet. It's a useful test. The more of the semi-obvious things you can uncover and fix before starting the real playtest, the more efficient your real playtest will be.
And let's face it, game companies don't even do blind playtest correctly, with a lot more resources. With a 1-man shop, you want to start that kind of playtesting only when you know you are ready.