Risk-free rate of return is around 4.25% right now. A money market yielding 5% would be a great place to park it till you figure out what you want to do.
Of course, this number will shrink if interest rates go down.
I'm old and boring so I'd probably stash it in VTI and let it do it's thing slowly over a decade. $400k invested correctly could get you to an early retirement, depending on your age.