If I have 1 allele in the mutable range, what's the chance of my children having huntingtons I am a girl, so I know it's less likely for 31 expand.

HD and Triple Repeat. With a 31 repeat allele, you still have a 50% chance of passing the allele to an offspring , and, as you know, the number of repeats often expands with meiosis and can mutate post meitotically. Disease is associated with an expansion>35 repeats, and the severity of the disease correlates with the length of the mutation passed on. In one study, 75% of "short" alleles expanded to threshold lengths.