I'm assuming you want a hotel closer to Disney since that where the majority of your trip will be spent. Like the poster above said, those hotels are further from Seaworld than Disney but it's not THAT far of a drive. Maybe 10 minutes, 15 minutes at most during heavy traffic.
With that said, the nicest place to stay would be the Gaylord Palms. But its extremely expensive. It's pretty much a resort.
Holiday INN Maingate east would be my 2nd choice....
http://www.visitkissimmee.com/leisu..._crm?id=202&name=Comfort-Suites-Maingate-East
Its in a somewhat secluded area and is right off 192 which has a ton of shops and things to do. The good thing about it is that, like I said, its in a secluded area and not right on the edge of 192 so hearing traffic at night shouldn't be a concern. You may face that noisy traffic at night issue if you choose some of those other hotels which are also on 192. There is also a cool pirate themed mini golf place right within walking distance of the Maingate East. So that could be something to do if you have a little extra time at night after your Disney or Seaworld visit. Old Town would be another area within walking distance. Old Town is a thrill park and has some cool thrill rides and interesting shops, however I find Old Town to be pretty dirty and wouldn't be a place I would want my young kids to visit if I had kids. Theres alot of smoking, and drunks, and just plain creepy people who hang out around Old Town.