If you want to pass some time,the beach is not far to walk,there is a casino and shops.
The Pegasus bridge is by the river,the original bridge,with bullet holes, the last time i saw it, it was in Norbert Dentressangles yard.
Cafe by the new bridge,Caen is about 6miles from the port of Ouistreham,where you dock.
I used to walk or bike it, on the path by the river.
Buses from Ouistreham to Caen, on a Sunday, may be limited.
Plenty of places to eat outside the port.
Or take a bike.