By the threshold of technology you mention (intersteller travel to habitable planets) you would certainly have the technology to grow and maintain an artificial womb. So you just stock the ship with self-replicating printing machines that can deploy artificial wombs, and have millions of frozen egg / sperm to populate them.

Really though, at that point, you might as well send the learning AI robots instead. Fleshy emotional meat bags with difficult to replicate reproduction are a liability.