This will be our first trip to Ireland and my husband wants to drive from Shannon to Co. Mayo on our arrival date. Any comments?
Shouldn't be a problem. Drive is about 2 hours depending on the specific destination, road is good most of the way and usually not that much traffic in the area.
Two hours? By what road? To answer your question, yes it can be done but I think you'll find it's longer than a two hour drive, particularly if this is the first time you'll be driving on the left. The mileage doesn't really indicate how long it will take, like you could estimate here. Even relatively good roads are narrow and tend to wind around so that you might find it difficult going as fast as the posted limit.
The N18-N17 route through Galway sounds like the 2 hour way to go, if you're in a hurry..!
Without knowing many details about you or your trip, I'd only comment that it's much easier to find things in the daytime if you've never been there before. If you're just getting off an airplane, give yourself plenty of time to adjust, stretch legs, collect luggage, rent car, use bathroom, etc. before making the journey from A to B. good luck! (ps. if you're getting in later in the day, have you considered stopping in Galway before continuing on?)