(before death, decedent remarried and name second spouse as income beneficiary of QTIP trust in addition to credit shelter trust; second spouse named co-trustee of both trusts with bank (which had the effect of replacing decedent's children); dispute arose between second spouse and decedent's children concerning trust accounting and decedent's estate plan; pursuant to settlement agreement, estate reimbursed parties for incurred legal fees; court held that administration expenses deductible as incurred by decedent's children, but that second spouse's expenses not deductible and that taxes incurred by estate did not reduce estate's marital deduction).