Torrylinn Shore, Kilmory
There are plenty of things to do and see on Arran, and although the roads might not be very fast, nothing is very far away. If you're feeling energetic there's rock climbing and mountain walking to be had in the north, and also plenty of walks of varying lengths and difficulties to suit every taste. Your hosts can recommend lots, and can let you borrow maps too. On a clear day, the reasonably strenuous walk to the top of goat fell is well worth the effort, affording views over kintyre to the Islands of Islay and Jura.
If it's golf you're into,there are 7 courses on Arran. The closest (and arguably the most spectacular) to Kildonan is the links course at Shiskine, by Blackwaterfoot. Shiskine is unique in having the only 12-hole course recognised by the Royal and Ancient. There are also courses at Brodick, Lamlash, Whiting Bay, Machrie, Lochranza and Corrie.
Brodick Castle is managed by the National Trust for Scotland and is well worth a visit not only for the castle building itself, but also for the beautiful and extensive gardens.
In Lochranza, in the north of the island, you can find the Isle of Arran Whisky Distillery, which went into production in 1994. They have a visitors' centre and tours of the distillery are available (with some free samples!)
Other activities available on Arran include Pony Trekking, Quad Biking, Fishing and Swimming (Pools at Auchrannie Hotel in Brodick and the Kinloch Hotel in Blackwaterfoot). For a rainy day, the Arran Heritage Museum offers a fascinating insight into the Island's History, and you can pop in for a piece of cake and a cup of tea in their cafe too. Also worth a look are the South Bank Farm Park, and the Standing Stones on Machrie Moor, as well as the numerous small workshops where you can watch crafts people plying their trade.

Brodick Castle

Lagg Hotel, Kilmory

Kildonan Hotel, Kildonan

Shiskine Golf Club

Lamlash Bay

Distillery, Lochranza