It's a lovely island and well worth exploring. A few highlights for me were:
Machrie Moor, which has six stone circles and some of the stones are over 5 meters high.
Kildonan (South coast) is where I spotted Otters on two occasions.
Brodick Castle, Garden and Country Park - some lovely walks, landscapes and scenery (castle closed until 2018)
Lochranza Castle - North West, lovely setting.
Lochranza area - red deer wandering around near the highway.
Enjoy your trip and fingers crossed on some decent weather.