Sharon, the cycle ride from Wadebridge to Padstow is wonderful. 5'5 miles each way, completely flat. I did it in June and I'm very unfit. They give you bike locks, so you can park up in Padstow and have a wander around. You could get fish&chips from Rick Steins on the harbour side (cooked so very little fat mmm)
The best cycle hire is Bridge cycles.
All my family live in Lostwithiel, so I'm there lots, going down again in October. It's been the worst Summer for ages, so hope it clears up for you. xx