Regardless of age, a new sibling can be very difficult for the child! How awful that some people think that he should be fine with this just because he's 11! Of course, he's going to have some insecurities. Not to mention, there's going to be this new person in the house who is going to disrupt routine, sleeping, and his parents for a while.
I don't know of any videos, but maybe they can check with their local library or maybe google the subject and find free online videos.
I also think that unless mom is planning on NOT breastfeeding, then their son should see a video about that as well (I highly recommend Dr. Jack Newman's DVD!!!). Even if mom is going to breastfeed, that doesn't mean he can't be included! We included our son, who was 27 months when I got pregnant, in EVERYTHING: ultrasounds, midwife appointments, online videos, DVDs and a sibling childbirth class. We were very frank with him about what changes my body would go through, where babies come from (maybe a more difficult subject for an 11yo), what sounds I would make during labor, and what to expect in the early days with a baby sister. Both my kids were born at home, hence the labor preparation.
I strongly believe that including him and allowing him to take "ownership" of his sister REALLY helped in the transition. He looked forward to looking at pictures of what baby sister might look like that day, was wonderful from the very beginning, and we've had VERY few issues (they're now 5 and 2). They have a great relationship and have since the minute she was born :) [He wasn't in the room when she was born (she came too fast), but Daddy brought him in about 2 minutes later.]
I think the best thing she can do is include him in EVERYTHING, including breastfeeding if that's her feeding choice :)