The person who wants to do this needs to sit down with a financial planner who can help with planning related to inheritances.
They need to discuss with this planner what their goals are, what their current and future financial situation is, and come up with a way to achieve those goals.
Moving money from the 401K into either a IRA, or taxable account can impact their taxes and can limit their options regarding transferring the funds to the next generation. It can even cause problems for them in the next few years if they need that money for medical expenses.
Unless they are under a deadline to move the funds from the 401K, they should take the time to sit down with a planner and do this right.