The Garlic farm is interesting and the cafe there does great food http://www.thegarlicfarm.co.uk/ Also really liked this cafe looking out over the sea near Ventnor http://www.steephillcove-isleofwight.co.uk/
Plenty of walking and a couple of National trust properties that are worth a look. I wouldn't bother with Black Gang Chine Theme Park, Your kids are probably a bit old for it.
Only been once was pleasantly surprised and will probably return one day.