Hello.
Firstly, watch out for the speed cameras from Taunton, downwards. When you join the A30 there is only one fixed camera (oncoming traffic side), so pedal down.
As TJ said, you have the National Maritime Museum in Falmouth. However, that is South Coast and you'll be on the North. Should take about 1 hr drive from Newquay. There are a couple of UBoat wrecks on the North Coast but I can't recall any visitor centre or such that detail these.
Other than that, just indulge in the local history by visiting the smaller coastal harbours etc, most have resisted the urge to develop and are steeped in History.
If it were me, I would look at the local Cycle trails and walks. Some of the best coastal walks are on the North Coast.
P.S When entering Newquay, don't be surprised to be stopped by Police. They are currently conducting random searches in a pilot scheme to stamp out public drinking and drug taking. I know the train stations are cordoned off, not too sure about the roads. Hide the Stash.
Have fun though. The weather is set to be great. I'll warn the locals you are coming.