My contention is exactly what you said, with the following added: The "further information" that changes their mind will be a change in their value system as opposed to information about the actual outcome of the situation (unless, granted, the actual outcome changes their value system).
In other words, if you change your mind later and decide "that earlier decision wasn't ethical after all" it will be because you have changed values, not because of additional information you get about the actual outcome. Additional information about the outcome might lead you to regret the decision, but I don't think it will lead you to decide it was unethical (because, as I contend, ethicality has only to do with intended outcomes, not actual outcomes).