Pressing charges against someone who has victimized you sexually can be empowering or it can be a nightmare. Not everyone needs or wants that type of closure (not that closure is ever a given in these cases, as many times the perpetrator gets off), and for some it can be more traumatizing than the original abuse, especially if it becomes a big public affair or drags on for years. It's a very individual decision for the person who had been wronged.
Now, this is a difficult situation because the person who was abused is not an adult. Polly does indeed have a responsibility to decide what's best for him. But I think all of the above should be taken into consideration before assuming that a court case will necessarily help her son.
On the other hand, it might help other young men -- if the ex gets labeled as a sex offender, it'll be harder for her to get into such a position again.
Tough, tough call.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.