Ireland isn't quite so hard hit and is clearing up faster it seems... It seems most transatlantic DUB/SNN flights are running just fine, just east/south-bound flights are being cancelled.
Unfortunately, it seems that your packages would likely be routed through UPS' Cologne hub or one of the UK ones, since there don't seem to be UPS/FedEx cargo flights from the US into Ireland. (Wikipedia claims DUB has UPS service from SDF, but with no references, and I can't find any such flights.) So you are probably indeed going to see some ash cloud-related delays.
Well, there's an Apple store a 20 minute walk from me. However, when I called on the 13th they said they didn't have any of what I wanted in stock, but should soon. If I hadn't gone to Prepared for Shipment today, there'd have been a decent chance they'd have gotten some in while I could still cancel, but it's not a huge difference. I understand not having all display types in stock, but I do find it kinda stupid that Apple doesn't let you customize things like RAM or HDs at the store. They can certainly do warranty replacements on-site for those types of parts, and even LCDs. I see no reason they can't ship extra RAM and some extra HDs of the popular sizes/speeds to the stores and let you have a same or next-day build. For people who buy Apple stuff at the store and forego some upgrade they didn't want to wait for ordering online, Apple's just losing out on easy profit by not letting the store do it.