here is a link to the local paper's listings etc. Sometimes you can get vouchers and discounts from there too, and there's an eating out section too. Minack definitely worth a visit if your children aren't too young, as it's quite steep. The beach at Porthcurno is v. beautiful too.
St Ives will be really really busy, and difficult to park at, but there is a park and ride train service.
If you want a bit of a quaint Cornish dinig experience, try a meadery, usually fairly child friendly. There's one at Newlyn.
The weather has been lovely this week, hope you enjoy yourselves