Not sure I see the difference between that and giving the Animorphs intelligence information, which they generally use to go kill Yeerks. And if Erek can give protection, by getting in the way, I think there were a few other missions where they could have used some of his protection.
How about if we humans promise never to hurt the Yeerks, and then the Chee can gently collect them all and build them a nice Yeerk pool on Mars, where they can infest non-sentient Martian animals?