Depends what you want to do in Okinawa. If you're thinking of just relaxing on a beach resort either on the main island or one of the closer outlying islands with an airport, then yes 3 days will probably be good enough. If you're thinking of sightseeing on the main island and going to other islands to enjoy the beaches and for snorkeling/diving, then you'd better plan on spending about a week there.
How many days do I need to enjoy Okinawa? Is 2 nights 3 days too few? We don't have too much time to spend in Japan, so trying to figure out the minimum time I’ll need to plan on.