I don't care what the physicians say about solid bones: At this age the skeleton is made of a special high quality rubber which even 50 years of yoga cannot replicate.
Oh and when they are tired I am convinced they could sleep on a bed of nails better than any fakir.
As the others have said: For HP5+ in rodinal this is almost grainless.
By the way when she's seventeen, don't choose that point to tell her she was on the APUG gallery at 9 months. Well, at least check your life insurance policy is up to date if you do.