I think this is one of those questions that could go either way. The Kribs might bother, hurt or kill some of the Guppies but then they might not. Depending on how happy and comfortable they are in their new environment. If you can provide lots of plants, caves and hiding places for them then I would say go for it and just monitor the tank for a little while. You will probably be fine.
I keep a breeding pair of Kribensis in a community tank with Guppies and Platy's (and others). There are various size juvenile's that also get introduced into the tank and they all co-exist without any issues at all. However, I did lose one guppy when I first introduced the Kribs to the tank but since then there's been no issues. I think the other fish in the tank now submit to the dominant Kribs.
Good luck with it all, Im sure you'll find that if you provide the Kribs with a comfortable environment then they'll be fine.
Cheers,
JS