The Caymans have their own currency, the Cayman Islands Dollar (KYD), which is pegged to the US dollar. However, you can pay in dollars (and with Card) in most places on the islands. The cost of living is about 20% higher compared to the United States.
The Little Islands, Cayman Brac and Little Cayman, are about 30 minutes away by plane from Grand Cayman; there are daily interisland flights. Cayman Brac also receives international flights.
Electricity on the Cayman Islands is 110 volt (same as US).