The IRAs will be subject to income tax when the funds are withdrawn, and withdrawals are subject to RMD.
To add to the above, the IRA's will be considered "Inherited IRA's" and typically there are 3 choices.
1. Lump Sum - all income tax due immediately
2. Five Year Payout - income tax stretched over 5 years
3. Annuitize it based on the beneficiaries life expectancy which will be subject to the yearly RMD.
(but now that I think about it, we had these choices because my moms IRA's were sitting with Annuity type companies - like ING). If your Moms is sitting at a bank, there may be different choices).
You will have to find out if it is qualified or unqualified money. Meaning, was it before tax or after tax money that originally went in. And don't take their word for it. Make sure you know the original source of the money. I say this because one company I dealt with, had the account coded wrong. It happens.
Companies may have developed other choices in the last few years. You have to speak to the company that holds the IRA. The IRA will be split into as many parts as there are beneficiaries. Each beneficiary can make their own independent decision.
It's not too early to get to work on this. It took me a long time to get the two companies my mom had IRA's with ...just to divide it into "parts".
If this IRA is invested in potentially risky assets, you might consider moving it to cash to protect the value. Or not. I depends on how you view where things are going. As Executor it is up to you to protect all assets. No one can fault you if you move it 'to cash".