Last Oct we did 5 nights at Poly. Loved it. We then did two nights in Orlando and went to Sea World. You can easily do everything in Sea World in one day. However, we didn't have enough time to do more "Disney" stuff: i.e., waterpark, DisneyQuest, more leisurely park visits, more time at Volcano pool, etc. This Oct we're using FTP to do 7 nights and get in all of the stuff we missed. No Sea World this time, unfortunately.
Depending on your family's desires and the ages of your kids, taking a day trip to SW could be a great idea. A waterpark and DQ (the stuff we missed before) may not work for you guys. And young kids will REALLY love SW!
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edit: If you decide to do SW (and the more I think about it the better it sounds), go to the website to get tickets. There are discounts for getting tix thru the website. I think I saved $5/ticket, and just missed the time cut-off for the $10/ticket savings. I don't know about your budget, but our cost was about $200 for tickets, food, and souvenirs (family of 4). I had to buy my daughter a shirt and my wife a whole outfit because they got drenched on Atlantis!