Can my step-son remove me as a trustee for no reason if my wife passes away??

The Special Needs Trust typically will have provisions setting forth the conditions and procedure for removing a trustee, and those terms will determine the answer to your question in regards to your stepson.  Typically, in California, a special needs trust beneficiary will need to more than merely state that a trustee should be removed.  The beneficiary may need to provide evidence to support his removal request.  Generally, a trustee can be removed for failing to perform a duty, mismanaging assets or no longer being able to carry out his/her trustee responsibilities.