A lot would depend upon routing.  If you are arriving via Limerick and Tralee, by car from the Dublin Airport, Google Maps says that it's about a 4 hour drive.  Personally, I would guess closer to 5. 

http://supermacs.ie/store/barack-obama-plaza-moneygall/  located on the M7, between Roscrea and Nenagh. is about 1.5-2 hours along.   It's an easy off/easy on Service Plaza.

A bit further on (Shortly after Limerick -- about 45 minutes - 1 hour past Moneygall) would be Adare, where there are ample facilities and car parking, as well as a lovely green / town park. 

Just beyond Adare, you pass right by a decent-sized Tesco.  I'm not sure what is readily available -- shopping-wise -- in the vicinity of the Tralee bypass.

There is a small, but decent sized shop located in Castlegregory   http://www.castlegregorykerry.com/castlegregory-info/local-businesses-castlegregory-kerry/44-lynch-s-country-store.html