I think your friend will do fine if you can impress upon him the importance of ignoring a schedule and let a combination of the weather and his and his crew's body and mental condition dictate the schedule.  He should not try to do it on a fixed schedule or in limited time.  He must not let a fixed schedule force him to take risks.  Doing so often results in bad outcomes for boaters and private pilots.  If he doesn't have the time or the demeanor to do what I suggest above he should not make the trip. All the best,