I'm originally from the north coast area, I don't live there now but all my family still do. If you can I would highly recommend hiring a car and driving up the coast road towards Portrush/Portstewart and on around to Castlerock/Mussenden Temple/Downhill or even up to Binevenagh for stunning views across Lough Foyle to Derry/Londonderry and Donegal. Cushehdun/Cushendall, Glenariff and Murlough Bay are all worth a stop en route but you may not have time to fit it all in!
If you're into GoT the Dark Hedges aren't far (near Ballymoney) and you'll pass Ballintoy on the coast road, which is the Iron Islands. Portstewart Strand and the dunes doubled for parts of Dorne and Downhill beach/Mussenden Temple for Dragonstone.
Even if you're not a GoT fan it's just a stunning coastline, there are so many incredible beaches - Runkerry/Portballintrae, White Park Bay, White Rocks/Portrush East Strand, Portstewart Strand and Downhill are all outstanding. You'll also pass the Giant's Causeway near Bushmills and the ruins of Dunluce Castle on the cliffs between Portballintrae and Portrush.
You're spoilt for choice with amazing independent cafés, coffee shops, bakeries and restaurants - Native Seafood, Harry's Shack, Coffee Hut, Ramore, Mermaid, Basalt, Neptune and Prawn, Harbour Bistro, Bean at the Beach, Vittle Bake Shop, Kraken, Amici, JamJar, Indigo, Morelli's ice cream are just some places serving amazing food, coffee and baking around the Portrush/Portstewart area alone. If it's open Roarke's Kitchen at Ballintoy Harbour is another gem. You definitely won't go hungry 