We enjoyed a little area centered around Key Street.....nice little places to eat, cute shops and street musicians (we were there several years ago right at the end of August). I think we were in Galway for a total of maybe 2.5 hours (mostly a lunch stop), so I cannot give much more advice.
But, if you do not get more recommendations for your time in Galway, consider driving up thru the Connemera region. Sky Road is listed in "National Georgraphic's 500 Journeys of a Lifetime" book, and it really is a pretty rural drive. While you could do the loop (over to Cong) in a day, it would be a really, really long day.
If you haven't been to Kylemore Abbey, that could be an interesting stop, if you break up the trip by staying overnight at least one night north of Galway..........or you could drive from Galway to Kylemore Abbey and back easily in one day.
But, potentially you have already planned something like that upon departing Galway.
How very lucky you are to have been to Ireland so many times, and I hope your husband finds it enjoyable, too.
EDIT: Just read the post ahead of mine. While I have not been to the Aran Islands, all my friends who have loved the Aran Islands....so that may be your best choice :)