You can make two separate transactions.
Go ahead and purchase your DC admission via the DC site, which would include your SeaWorld and Aquatica tickets. Pay via credit card and print your confirmations.
Then decide what day you will be visiting SeaWorld, as your Quick Queue is valid for a certain day that you select.
On the SeaWorld site, click on the Quick Queue button (via the link in my previous message) and add the Quick Queue to your SeaWorld cart. It will ask you to select your date (use the date of your planned visit). Enter your payment information and you will be good to go
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