In reply to MikeR:
Trip on the Steam Train. My kids loved it when they were that age, everyone waves as they go past.
Paddle on the shore at Loch Morlich and playing on the beach/in the trees. We hired a rowing boat for half an hour (easily long enough for a toddler).
Highland Wildlife Park is a really good day out, as is the Newtonmore museum - most of it is outdoors with buildings you can go in, and an old fashioned sweetie shop.