I haven't been to Legoland, but I'll speak to Sea World. The only problems an overweight person might have at Sea World is the rides. There are three rides - Wild Arctic, Shipwreck Rapids, and Journey to Atlantis. Wild Artic is a motion simulator, much like Star Tours (but not as rough), Shipwreck Rapids is a water ride, much like Grizzly River Run, and Journey to Atlantis is a roller coaster. My only suggestion is to go to the parks and see it and decide if you'd be comfortable. There is also a gondola that you can pay to ride which might provide a challenge depending on one's size.