There is no income tax benefit to giving away your assets to Charities at death as opposed to during your life.
If you create a Charitable Remainder Trust the Grantor gets an annuity for life, and at death everything goes to the charity. The amount of the gift is the present value of the gift based upon the life expectancy of the grantor and the amount of the annuity. You receive an income tax deduction for the value of the remainder interest. You can also use this in combination with the Irrevocable Life Insurance Trust, by using the interest or annuity from the Trust to pay for a life insurance policy that you then place into the Life Insurance Trust for your children. There is no three year look back period for the Life Insurance Trust because the Charitable Trust bought the life insurance policy, not you, and the proceeds of the life insurance policy will pass outside of your estate.