Going to a graduation ceremony in Dublin at 1pm with a party of 4 and it's on a Monday
I expect the event to be finished by 2.30 so it's an awkward time, too late for lunch and too early for dinner as most places don't open up until 5 and some I found even close on a Monday :-(
Odessa, Dame Court, might suit you. They do lunch 12 to 4. I have been there for evening meals a few times, and I like it.
Depends whereabouts your ceremony is, but there are a couple of nice places around Dawson St/ Grafton St general area.
I like Farm on Dawson St, it's open 11 a.m to 11 p.m. according to their website. Enjoy the day!