I-526 takes about that long and you'd still need an I-601A. All in all, for you just following to join would be easier, cheaper, and probably faster.

For your parents, same issues as for you apply, so if one of them were to do an EB-5 they'd still need an I-601A, now, they're presumably married to one another, so unless there's a grampa or grandma up there that is a USC/LPR that's dead in the water. Unless they want to try the 245(i) angle.