Starting to panic a bit

We are going to Hawaii this month for my birthday. First time going and my main motivation above all else is seeing pearl harbor. I tried to reserve tickets to when I booked months ago but it said that I had to wait until closer to the date. I just tried to reserve tickets now (three weeks out) but the website said they weren't reserving tickets, but to please bring our tickets with us when we visit. Huh? I'm so confused and a little panicked that we are going to get screwed out of the sole purpose of our really expensive trip. Anyone have any insight or ideas?