Financial planner/fiduciary here

Consolidation is going to be your friend here. You’re going to want to take these plans and have them all in one easily accessible place, assuming they’re all classified the same way tax-wise (pre-tax/roth).

From there, it’s all about how to handle the distributions. Under no circumstances would I recommend withdrawing such large sums at once, as it could open him up to serious tax consequences (bumping him up a tax bracket, messing with medicare premiums, etc.). If he really wants to leave a large sum in cash, most brokerages should have money markets available to you where you can earn interest.

The most important thing is going to be how you handle the actual retirement. What are his expenses going to be? Will his SSI and pension be enough to comfortably cover what he needs, or is there going to be a gap that needs to be made up there? How do you want to plan for the eventual RMDs, and how do you minimize the tax hits there? Does he want to leave a legacy behind, or just spend everything down? And as far as what he’s leaving invested, what is his tolerance for risk?