Legal Question in Wills and Trusts in California

There is no black and white answer to the word "reasonable." You were selected as trustee because your family member trusted you to use your judgment. So the word "reasonable" means "reasonable under the circumstances." If it would be reasonable for your niece's parents to have bought her a Honda Acord, and that purchase makes sense in light of the funds remaining for her college education, then you can feel comfortable with that decision. If it would be reasonable for your niece's parents to have bought her a C class Mercedes, and that purchase makes sense in light of the funds remaining for her college education, then you can feel comfortable with that decision. Make a note in your records of what factors you took into account in making your decision. You do not have to make the "perfect" decision, whatever that is, assuming there even is such a thing. You are supposed to make a "reasoned" decision.