Parent left no beneficiaries listed on Trad IRAs- Distribution Options / Tax Rates?

As a legal representative of an estate where a parent left two IRAs with no beneficiaries listed, there are so many different answers from both the IRA custodian and even tax people.  The attorney advising states that (this is state of Florida) that the estate must distribute all assets by 12 months of date of death, but I've also heard that non-desigated beneficiaries of IRAs where RMD distributions have not yet started are eligible for the 5 year distribution period to string out the period by which to pay taxes on these IRA (which are quite large approcx 1 million). Also, tax rates are hard to get a fixed answer on too. One source says IRA distributions can be paid directly to the estate beneficiaries at ordinary income tax rates, while another proposes that the IRA assets will have to be taxed at the majority estate income tax rate of 39%. Who is right and who is wrong? Looking to have the two beneficiaries pay the least in taxes and extend the distribution period as long as the IRS will allow. Someone please help!