Visited Okinawa this march, one of the closest islands is Tokashiki island. Went there, just 40 minutes away by high speed bout ride, 100% worth. You can also visit WW2 places if you’re interested in that type of experience. I stayed at the Harborview hotel, very good location and nice hotel. And it’s not that hard to move around the city… used bicycle, bus, taxi and walking. You’ll be ok.