6:30 Fantasmic will be done around 7:00, but You & 7000 people will be leaving at the same time, so unless you sit in the very top row & are among the first out you can expect it to take anywhere from 10-20 minutes just to get to the street in front of the theater...then you have to get out of the park, with most of those same people who of course will also be heading for the boats & busses. If you're ahead of the pack & walking quickly, it can take you 10 minutes to get to the path or the boat dock. So, say you are at the top of the theater & get out first at 7:01, then 10 min. walk to the boat or path. Then 20 minutes to walk or boat. The earliest you could possibly get to Captain's Grill would be around 7:30. Would not count on that unless you are very quick, though. More realistic will be you're caught in the crowd & takes you 20 to get out of theater & another 20 to get in line at the boat, then wait for the boat...
So, two choices...walk from DHS to Yacht Club--at least 20 minutes. Or take the boat...and that will be entirely luck of the draw how quickly you'll get on - you could be facing massive lines for the boats...or be first in line. Then the boat ride can take 20 minutes, too.
Bottom line, I would not schedule dinner at Captain's Grill before 8:00 p.m. Chances are if you make it there early, they'll be able to seat you (same is true if you're late.) Allow extra time if you're traveling with small kids in strollers, too...can't take the strollers into the theater, so will be a mad dash to get the strollers when show is over.
