Thanks for your great question, Jenny!
Yes, the Pirate Adventure is still offered at the Grand Floridian. According to the WDW site...
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Disney's Pirate Adventure is a 2-hour sailing adventure for children between the ages of 4 and 12. The adventure takes place Monday through Saturday from 9:30 a.m. to 11:30 a.m.
At the start of the Disney Pirate Adventure, children are given a Mickey Mouse-inspired pirate hat or bandanna to wear as they make their way onto a boat, which is bedecked with a high-flying Jolly Roger flag blowing in the wind. Setting sail, the group takes off to exotic ports of call—nearby Resort marinas—as they join In a hunt together to collect buried treasure.
During the expedition, participants will enjoy lunch (which includes a peanut butter and jelly sandwich, gummi bears, krispy treats and juice), learn how to talk like a pirate, and—if they're lucky—return with a bag of genuine pirate booty."
The cost (as of April 2010) is $36.21 (tax included) per person.
In case you prefer, a very similar cruise is also offered at the Yacht and Beach Club (Mon, Wed, Fri at 9:30am), Caribbean Beach Club (Sun, Tues, Fri at 9:30am), and Port Orleans Riverside (Sun, Tue, Thur at 9:30am)
For reservations up to 180 days in advance, call 407-WDW-PLAY (939-7529) (Note: when you call, don't select any of the phone menu options, select option "1" or just hang on and a Disney representative will answer the call)
Hope that helps!