How much can the juvenile form of Huntington's Disease be anticipated?

Good evening,
my mother-in-law is at risk for Huntington's Disease: her 2 sisters are sick, she is fine at the moment but despite being 75 years old I know that the risk remains since she will never do the test (she is convinced that she is healthy).
The sisters both had a late onset, I think in their 60's, and they are the first and, at the moment, the only ones to have manifested the disease in the family.
My husband is 42 years old, asymptomatic and even he has not done the test ...
Unfortunately the news of the disease came when we already had our son who is now 11 years old... Since I discovered the genetic anticipation and the fact that there is a variant of juvenile disease I keep on worrying for our child, constantly observing him and looking for any symptoms ... I tried to get help from a psychologist but nothing seems to work.
My question is whether the juvenile form usually affects boys whose fathers in turn have fallen ill young enough or can anticipate so much that it can occur in the child before the parent and grandfather...
The idea of my husband taking the test scares me because I would not be able to take a 50% risk for my child.
My son is fine, he's an intelligent and sporty child but I can't help worrying about his future.
Thanks for your time

The disease can anticipate, also significantly, but it is not the case to be overwhelmed by anxiety. Talking about it in person can help you overcome the construction of a castle of anxiety. If you wish to visit us in the clinic, you are welcome. You can contact us at the toll-free number 800.388.330.