We used to pop to Cornwall all the time, very nearly moved there next to a Llama trail owner!!!
We also stayed in Polperro, lovely little place but twisty roads,that bit about Lusty Gaze reminded me, we stayed in a hotel overlooking that, it was hot and beautiful!!
All paid for attractions are expensive with a family in tow, the best thing is to look out for offers and deals with things like Groupon etc, or take packed lunches and drinks.
The reasons behind some of the high entry fees are the cost of the public liability insurance in these sort of places...its such a shame!!! To take a family of 4 anywhere you are looking at spending at least £50
Love Cornwall