I haven't been to KD or CW but have been to BGW, and in addition to what @AmyUD06 said I'd add:
- I didn't use Quick Queue on my trip, although I went on a Tuesday in August. The longest line I remember waiting in was for Le Scoot. I don't see a downside to waiting to buy Quick Queue, especially if you don't end up needing it.
- BGW opens in phases in the morning, so if you want to rope drop it just be aware of that. I thought the order was England before the stated opening time, Scotland, Ireland, and France at the posted opening time, and then the rest of the park 30 minutes after the opening time. I could be wrong though on this though, can someone clarify?
- Full day would be great at BGW, adding the half day would also be cool, but would only do it if you want re-rides or want to do everything in the park.
- Don't sleep on Le Scoot, the train, skyride, or Escape from Pompeii (you don't get as nearly wet as on other shoot the chutes). All of them are fantastic gems at BGW.
- If you like history I would 100% recommend Colonial Williamsburg. It's not all that far away, and it's easily the best "living history" museum that I've been too. You can pay to go inside the buildings or go on a tour, or you can go to the visitor center and walk around the streets for free. You could use your half day here if you wanted.