If you are a single bitcoin investor, would you rather teach a trusted family member about Bitcoin than involve your personal lawyer. I ask this because I grew to understand that lawyers are good at handling confidential issues like Wills.
The duty of Lawyer is to ensure wills are followed strictly, but leaving your bitcoin totally in the hands of a lawyer is entrusting it to a third party totally which is wrong, additionally leaving it in the hands of only a family member poses the risk of him taking all your funds when you are gone.
A good option might be creating a multi-sig wallet, let the family member be part of it as well as your lawyer, that way the family member cannot take it all for themselves and the lawyer must ensure your will and distribution formula is strictly followed before he authorizes transaction.