Do both husband and wife have to be at least 59 1/2 to avoid early withdrawal penalties from 401k? Or just the who has the 401k? Will we need to file taxes separately?

No. If the spouse who is at least 59.5 years of age, then the distribution from THAT spouse's IRA will NOT be subject to the 10% Early Withdrawal Penalty.

Just make sure you are in fact 59.5 years of age when you request the distribution. A client of mine made the mistake of thinking he could request the distribution in the YEAR he turned 59.5, and request the distribution too early, and got hit with the 10% penalty.