in the event my wife predeceases me there are five beneficiaries. I would like to remove two of the names. Can I do this with a Codicil?

If you have a Will that names beneficiaries in case your wife dies before you, then you should be able to either execute a codicil or a whole new Will and make the desired change (assuming you are still mentally competent - I assume you are or you wouldn't be posting this question). If you actually have a revocable trust or an irrevocable trust in place, then it may be a different answer. You should also check all beneficiary designations to ensure they work as intended. My best advice is to get an estate planning consultation with an attorney who can help you figure out what you need to do to ensure that your desired change gets made.