if this round of plants is going to be outdoors, i would honestly just plant em in soil. I have experienced signifigant recovery time transplanting hydro clones to soil, like a week sometimes. If they are going outside anyway and you cant use clones, then i don't see much of a hydro benefit. You could, as allready stated do ebb and flow in rokwool that can be transplanted to soil. But if you have a few weeks to let em gro in soil indoors, it's much easier, first-time freindly, and hardly that much slower at that stage of growth, imho.
you can buy feminized seeds for more $, but there is no way to tell if any certain seed or plant is male or female until it exhibits it's sexual characteristics. This occurs naturally after the plant reaches maturity in veg state. This is also characterized by the nodes becoming asymetrical, as in branches that stop growing on opposite sides of the plant. To tell early, wait till you have a few 2 inch long branches, cut one, root it, and stick it under 12/12 to initiate flowering. Or you can potentially cover a branch on a plant under 24hr light for 12 hrs a day with a lightproof paper bag for a few weeks.