They may be very threatening and rich but neither his family, or their scion, is above the law. However, I would suggest you put your trust in the justice system in abeyance until such time as it's seen to be done as there's nothing to be gained by attempting to predict the outcome.
I would suggest that, if required to attend, your daughter is accompanied by your husband and her big brother as that will at least demonstrate that she is not without, as sexist as it may sound, male protection - abusive males may think twice if they have reason to believe they may find themselves receiving what they intend to mete out.
I would expect that one of the police officers who attended the incident will give evidence and that his/her account will go some way to corroborate those of your daughter and her friend. Your daughter will simply be asked a series of questions by both the prosecution and the defence to which, needless to say, she should give truthful answers and resist the temptation to elaborate.
As your daughter has given birth, she'll know that there are far worse things than being cross-examined by the likes of wheelson 
and I suggest she discreetly holds a little photo of her ds to focus her mind on the need to protect him at all costs.
I recommend that she requests a screen as this, contrary to what I erroneously wrote in my earlier post, will prevent her from seeing the accused or having the little shit him make eye contact with her.
I really feel for you and your dd and I hope you'll update this thread as and when events unfold,