I know I'm replying years late lol! But I'm going to leave some info here for the next person that comes looking!
-eat at Zizzis for the BEST vegan pizza you'll ever have! As well as tons of vegan options easily listed on the menu. They even have vegan dessert options- including a heavenly chocolate tarte with coconut icecream.
-Chopped for healthy fast food. You can create salads, wraps, etc. They have tons of veggie options and even tofu. I had a wrap which was delicious and filling.
-The Rolling Donut for amaaaazing vegan donuts. Unique and traditional flavors.
As far as things to do- check out the Trinity College Library (the Long Room). Its absolutely stunning. The campus is pretty as well.
And definitely take a day trip to Giants Causeway. Unique and beautiful. Unlike anything else.