Take a pot woodburner, forage some muscles from the beach ( mud) or round the side of the castle and cook them then either round in th nature reserve across the bridge or across the estuary at diganwy.
Conwy mountain is close and always a laugh, nice views of llandudno schicent pass, Anglesea, the coast. You could even go up it at night, a quick walk.
You could try the church in the centre of Conwy, easily passed by and also definatley take a drive up to dolgarog dam on carnog llewellyn, a lot of gates so you could drive up another road and walk over (if the outdoors are your sort of thing) it burst in 1900 or something and killed 100 people, huge boulders washed around.