Here is an idea, plant them in containers until they get a bit of size to them, then take a clone from each one and flip the clones to 12/12. They'll show sex within a couple weeks, and you haven't shocked the whole plant. As was pointed out, 1 gal pots work well, but if you are doing an outdoor grow, and I'm assuming you wanna plant directly into the ground, I'd put 'em every 2' at the closest. 3' would be better to me, but then I'm an indoor kinda guy, so take my advise for what it's worth.