Enfied is bypassed (not great). Loughrea, Ballinasloe are trouble spots. Traffic from Oranmore to the city centre will be a mare. If I was you, I'd see if you can get a room in the Forster Court hotel on Thursday night (2 mins from Radisson at a fraction of the price). Go to the Malt House for dinner. Then take in a band in the Kingshead, or have a pint in Freeneys. I'm heading for Galway myself this weekend.
Driving at that hour of the morning (4am or so) is dangerous, as you will be tired. I've done it myself before, it's not pleasant.