For a truly authentic St. Patrick's Day meal, don't served corned beef and cabbage, which is in truth Irish-American rather than Irish food. Instead, serve roast lamb, which many true Irish eat on their national holiday. Mint sauce (which is, after all, green) goes very well with it.
Speaking of tips, one beverage that goes very well with Irish food is the smooth-flavored Tips Tea. This is a brand that, like Barry's Tea, is truly Irish, which makes it difficult to acquire in the Americas. However, it travels well through the mail, so don't hesitate to order some online.