Replies to comments since my last post:
@TexasProud, I believe Dad Does' intent if John Doe predeceases would be that John Doe's portion would go to John Doe's kids. This is unlikely to happen, but it is another reason to add "per stirpes".
@Sunset, I believe the gifts would be subject to the annual gift tax limit.
@pb4uski, the kids currently are in lower tax brackets but will eventually be in higher tax brackets as they get (hopefully good jobs) as young adults. Good point. The amount involved wrt to the Roth is mid six figures. Regarding your next post, I have wondered about partial disclaimers and will mention that to John.
@sheesh1, there is a will (and two trusts), but in the case of the Roth IRA and the traditional IRA, they both have beneficiary designations, which technically override the provisions of the will and trusts as I understand the situation. Although it's really a distinction without a difference, as the will and trusts all say to split things equally among the three children (the will specifies per stirpes, I believe the trust documents do as well).
@MooreBonds, regarding your first suggestion in your first post, John Doe is concerned that his own estate will exceed the estate tax deduction, either through good investments and a long life, or through a change in the estate tax structure by the government. Regarding your second suggestion in your first post, this would eliminate the stretching/sheltering of the Roth IRA. Thank you for your comment about college aid; I had not thought about that angle.
@MooreBonds, regarding your second post, my understanding is that listing a trust (or one's estate) as the beneficiary nullifies the stretch IRA provision. [1] So in this case although there is a trust also, it is not listed as the beneficiary for this reason.
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[1] It is possible, according to an attorney I know, to set up a trust to enable the stretch provision to remain on Roth IRA assets placed inside the trust. But they are difficult to set up / easy to get wrong, so it was advised against in another part of the Doe estate.