Our planet is dying. Cliche, I know, but unfortunately true and we do not have superpowers or the technology to build generation ships to escape. We have maybe a hundred years left, and we have decided that our best hope of leaving a lasting imprint on the universe is to try to make sure life does not die out, should it be that our planet was the only one on which it ever developed.
To that end, we have identified several nearby(ish) star systems with candidate habitable worlds and wish to create automated spacecraft that we can send out to bring about life on those worlds. Our technology level is roughly the same as modern human technology and our biochemistry is surprisingly similar (DNA, RNA, proteins, carbon-based metabolism, etc.)
What should go on the spacecraft to give the best chance of life taking root?