Our past two visits to Orlando had to include Seaworld - not because of Seaworld, but because my folks LOVE Discovery Cove and you get a 5-day pass to Seaworld with the cost of a day at Discovery Cove. Both are great parks for a break from the larger parks. There isn't so much running around, Sea World is smaller, half of your time is spent sitting at shows, not standing in line for rides or walking large parks. If you find the time to do it, and you've never been, I'd say it's worth it and you should choose the day you think you'll be most tired and wanting a break from all the running around.
We are going down in November, but skipping SW this time... it's enjoyable, but because so much is show-based, it doesn't change and it's too old hat - there's just not the repeat thrill in canned shows as there is in rides! I will say the shows are very well done - especially, and surprisingly, the Pet Show (cats, dogs and such - you HAVE to see that one to believe it...) If I'm recalling the right park they also added a kind of Circ de Soleil performance last time that was very entertaining (and air conditioned!). What wasn't impressive was the Dinner with Shamu, for us at least... it's dark and basically you're just eating a very expensive dinner while a whale swims by the restaurant area.
The animal exhibits are enjoyable... it's kind of a pain to do the dolphin feedings because you have to stand in a very long line to buy like 4 mackerel to feed the dolphins, and it's at set time (obviously they can't feed them continuously). So plan on one of you standing in a long line for fish while the other entertains the troops (and there may be a purchase limit per person in line, so check that too).
That's about all I can recall. I always thought you were paying for a show or two and that's all SW was about, but they've definitely realized that they needed to have a lot more to entertain people when they're situated right next to DW and US...
Oh! I forgot about the kid play area, that's real nice too... and well monitored by the staff, so the parents can rest up!