Ed Slott: How Many Beneficiaries Can I Have for My IRAs?

Q: I have two Roth IRAs at separate brokerage firms. I want to name my wife as beneficiary for one account and my son as beneficiary for the other.

When I die, can my wife convert her account into her own Roth IRA so she does not have to withdraw the money in 10 years? My son (he is above 18) will get the other account, and will have to withdraw the money in 10 years.