We love Seaworld, and WDW. We also love Universal studios, Islands of Adventure, Busch gardens, Discovery Cove and the waterparks.
In your situation I would say to skip Seaworld, and devote your time to WDW. WDW time is too valuable to give up a day, and pay extra to go to another park. With only a week in WDW, you should stay put.
What works for us, because we love ALL the parks.......
We alternate between WDW, and/or all the other parks every other year.
Last year we did all things WDW, including all 4 park , water parks, Disney quest, and Downtown Disney.
This year we are doing everything on the Orlando Flex Pass Plus. Includes Seaworld, Busch Gardens, IOA, Universal, Aquatica, and Wet&Wild. 14 days of unlimited use at every park. Ironically we will still be spending some time at our Favorite WDW Resort, The Polynesian. We plan on relaxing at the Poly and enjoying the resort, without the pressure that we have to do the WDW parks.
Next year we will be doing the WDW parks again. It works for us, but we also do 2 weeks in Orlando. We are never rushed with our schedule.
With only 1 week in WDW, I think you should spend that valuable time in WDW, and enjoy it. Dont worry about missing anything. There will always be another time for Seaworld.
Good luck with the decision.....
Syndrome