That's a fantastic area for cycling, and three days won't be enough!
There is a traffic free cycle path (a PROPER one, with a billiard table surface unlike the poor relation UK equivalent) which runs from the ferry port at Ouistreham all the way into Caen. It runs alongside the river, passing Pegasus Bridge.
There is a nice ride from Caen out to Arromanches, and the beaches are all well connected by quiet roads/paths.
Google the "route du cidre" which I particularly liked. There are plenty of others. If I was at home I could look up the cycling route map of Calvados that I bought, but I'm on my wanderings just now. Try googling "Calvados a velo" or similar.
Edit... It's
Le Calvados a bicyclette. There must be about 40 routes of varying lengths marked out on that map IIRC..