We had asked a swim team coach who worked with my S2 for 6 years. Luckily he was able to get a nice letter out pretty quick. Many have used a family member. I think that by sending the recommendation it is another way to show interest in the school, and not act as if it is a fall-back safety to an ivy/more selective school.
Here is a thread from last year about this topic:
http://talk.collegeconfidential.com/university-rochester/1709094-how-important-is-the-family-recommendation.html#latest