Wow my family loves Seaworld but have only been 2 trips, because it is kind of expensive (vs. spending the extra days at WDW). The first trip the kids were 6 and 8, I think. They loved petting the stingrays, feeding the seals, and seeing the Shamu show (where, BTW our trusty camcorder gave up the ghost after being drenched by Shamu's wave goodbye). My older girl (as well as hubby and I) loved Kracken and Journey to Atlantis, but we did wish there were more rides. Got our tickets tamped for the second free day, but never made it back
Last trip (kids now 10 and 12), we went two days and I have to say my kids loved it as much if not more than WDW and US/IOA. We saw all the shows (which are wonderful BTW- especially Blue Horizons), went on the few rides, enjoyed seeing all the sealife at a relaxed pace and
fed the dolphins.
THIS was the highlight of the whole trip for them. They each brought home a picture of themselves feeding a dolphin and those pics are displayed in their bedrooms to this day! Now that they have Manta we can't wait to go back, but sadly won't have time on our WDW trip in Oct/Nov. Guess we'll have to book another trip soon!
So yes, for our family it was totally worth it, but like others have said it depends on your family. Your kids are young so they won't be going on the rides we went on but they do have a kiddie section now with some kids rides, and the 4 year old will have a blast in the climbing net (if you let him/her). The shows are fantastic, though I'm not sure how much the 1 year old will be able to take in. But if if it sounds like a park you and your hubby would enjoy go for it- You won't be disappointed!