Is it OK for me as rabbi who is officiating at a wedding to use a Kesuba which has English translation after the signatures of the witnesses.

Yes, however the witness should not sign the English.

The reason why it’s OK, is because it says clearly that it’s not a literal translation, thus any discrepancies between the two do not matter.

שו”ת אג”מ אה”ע ח”ד סי’ צ. וכן כתב במשפה”כ ח”א ע’ רסו ואילך.