Retired NYC teacher IRA - take large withdrawls to lower estate tax?

My mom's IRA is about 800K which puts her into the 37% tax rate if she leaves it to the 2 children.  Should she take a large chunk now (say 300K)  and pay lower taxes on that and then the heirs pay less on less inheritance?  Or will it be 400K each that are taxed?  

She doesn't need the money to live on and she's in her 80's.  Thinking of tax purposes only.