I agree with DisneyQuest, especially CyberSpace Mountain (build and ride your own virtual rollercoaster). We hit CyberSpace Mountain just before it opened and got to ride 4 times before there was any kind of lineup! It was one of my son's favorite rides and you can buy a video or DVD of yourselves riding it afterwards! The Buccaneer's Gold pirate ship shooting experience at DisneyQuest was pretty cool, too, and so was AstroBlaster. You could spend a whole day there is your stomach and nerves can handle it-a level 5 CyberSpace ride and the noise of the place got to me but there are quiet places with couches and coffee upstairs. Take Advil, Gravol and some earplugs and go enjoy yourselves!
For outdoor fun there's the trail rides at Fort Wilderness (for ages 9 and up) and you can rent bikes there too. There's Mouseboats at the Disney lake resorts (need to be 12 and up to drive alone) and there's snorkelling among the fish at Typhoon Lagoon. Actually any water park activity would be great for an 11-year-old.
My son really enjoyed the Pirate Cruise for kids up to age 12 at the Grand Floridian (open to anyone, not just GF guests) but he was only 8 - not sure if an 11-year-old would get into it.
