Hillary Clinton will also help out, standing in for her convalescing husband at some ceremonial events when she returns from her trip to Africa next week. But aides don’t want the First Lady to be seen as usurping the role of the vice president as chief surrogate. Clinton is expected to postpone two major foreign trips: a visit to Mexico has been delayed until mid-May, and an eight-day Latin American tour will wait until fall. For now aides are looking for ways to distract the president from his troubles. ““We hope he learns to love to swim,’’ says one. ““And we’ll make sure there’s plenty of time to watch basketball.''