We go down to BVI through the ferries 5 to 6 times a year. Assuming the ferry gets you there at 11 am. I would say the time frame works. Concerns are if the ferry is on time or even canceled. In the last year, we never needed 2 hours at the airport. That being said,,,, we always take the 7:30 am ferry. Id rather enjoy a great breakfast, window shop, and be bored at the airport than the stress of not being able to get to the airport on time.