When will you be on the Grand? We're on the 8/17 sailing. Kimjack is correct - visas are not required for any ports except for St. Petersburg. If you tour with a shore excursion from the ship, or with a company like Red October, they get a group visa. You only need a visa if you tour there on your own.
Lots of baltics itinerary information to be found on cruisecritics.com message boards. Go to ports of call and then baltics.