Newquay itself is pretty manic and touristy, but there are nice bits and you've got some really great places within reach. Plus if you surf theres tons of that. Where are you staying?
My favourites are:
Walking the coast path - really amazing scenery.
Theatre at the Minack - an open air cliff side theatre. An incredible experience.
The Eden Project is a good day out.
Port Isaac is a gorgeous little fishing village. I wonder if the chocolate shop I loved when I was ten is still there?
The Roseland Peninsula - you go just south of Truro and get the King Harry chain ferry, the other side is full of beautiful scenery and pretty towns.
Padstow is nice, and home to the Rick Stein empire. His fish and chip shop is relatively cheap (for him!) and pretty delicious.
St Ives is also lovely, the Tate St Ives is worth a look and also has the Barbara Hepworth sculpture garden.
Eating out! You can't move for places to eat in Cornwall. Rick Stein, Jamie Oliver, pub lunches, seaside cafes, there are so many options. You're spoilt for choice in Newquay, but one I like is Viners its nice, kid friendly and quite near you..
Lastly have fun, and say hello to Cornwall from me. I miss it!