I can't think of any true rights that aren't protected by the Constitution.
On the subject of a child visiting a parent in prison. I would argue that having been deemed unfit to exist among society, and hence being locked up, they are clearly unfit to raise a child, and by committing a crime have forfeited the right to do so.
I said kid, not child. No one can raise a child from prison, but it's pretty hard to argue that a 12 year-old, or an adult 35 year-old visiting a parent in for life, is some how responsible for the actions of the parent.