Drat, have only just seen this and it's probably too late - but we went in May half term and loved it there.
Just in case you see this, I can recommend the Sunset Surf cafe on the beach. Also, go to St Ives and visit the Tate. Porthgwidden Beach Cafe there is lovely for lunch and not as busy as the Porthmeor Beach one.
There's a little retail park down the road with an M&S, Boots etc which is very handy.
Minack does kids' story sessions one morning a week I think - but we were so lucky with the weather we didn't do much more than hang out on Gwithian beach - the rockpools are great fun for kids.
But all of this I am sure you will have discovered for yourself. Hope you have/had a fab time, we completely loved it there and hope to go back next year. 