It’ll be summer so definitely visit the Na Pali coast either on a boat, or by the Hanakapiai hike. If you want to see really really beautiful water when it’s clear and calm with no waves, stay on the north shore. The south side will have summer swell and waves. Go to Kokee state park for the best hikes. You should definitely try Acai Bowls here in Anahola at Kalalea Juice Hale or the shave ice in Kapa'a at the Wailua shave ice truck.