Well here's my two cents worth.
When I was a young lad, St Patrick's day would start off with a brisk stroll out to the country side. My father would brings us down to the defunct railway line by the river Suir, where his father used to bring him to find some shamrock which we always did.
We would go home and then later on head into the parade. After the parade we would go to the pub where my father would have no more then two large bottles, off the cooler of course, and we would have a coke and a bag of crisps. off home for dinner together and then out on the street to play with the other kids.
We are a Roman Catholic family but we never went to Mass on St Patrick's day as my parents decided that since it was in Irish we didn't have to.
How about keeping it nice and simple. A stroll out along the local beach, maybe a picnic later?