Outfielders Franklin Gutierrez, Michael Saunders and Casper Wells, third baseman Kyle Seager, catcher Jesus Montero, shortstop Brendan Ryan, starting pitcher Blake Beavan, closer Tom Wilhelmsen and reliever Carter Capps are the current players who've committed at this point.
The four prospects taking part will be catcher Mike Zunino, last year's first-round Draft pick, along with infielders Nick Franklin and Stefan Romero and pitcher James Paxton. Romero was the Mariners' Minor League Player of the Year last season. All four of those youngsters have been invited to Spring Training next month in Peoria, Ariz.
Also appearing at FanFest will be manager Eric Wedge and general manager Jack Zduriencik, along with former players Jay Buhner and Dan Wilson.
All the players will participate in question-and-answer sessions with fans and be available for autograph sessions.
Among this year's highlights is a new 200-foot zip line ride through the Safeco Field outfield as well as a "Felixing" photo opportunity for fans who want to put themselves in the image from Felix Hernandez's perfect game celebration.
Fans will also be able to run the bases, tour the Mariners clubhouse, try to hit against a simulated Felix fastball, play catch in the outfield, view memorabilia from the perfect game and last year's combined six-pitcher no-hitter and swing a game-used bat.
Fans will also be able to get their first look at Safeco Field's offseason ballpark improvements that are currently under way, including construction of the new outfield walls, the addition of an Edgar's Cantina and Lounge down the left-field line and installation of the new video screen in center field, which will be the largest in Major League Baseball.
Executive chef David Dekker will offer a "Taste of Safeco Field" in the Diamond Club, cooking up the variety of dishes available around the park and showing a sneak preview of what will be on the menu at Edgar's restaurant.
Former Mariners beat writers Jim Street and Larry LaRue will be at the ballpark with their recently released books, doing readings and offering autographed copies. Street, who covered the Mariners for the Seattle Post-Intelligencer and MLB.com until retiring in 2010, has just released "Life From the Press Box."
LaRue, who covered the Mariners for the Tacoma News Tribune from 1988-2012, released "Major League Encounters" in April.
FanFest tickets are $10 for adults, with kids 14 and under getting in for free. Tickets are on sale at mariners.com/fanfest and at Mariners Team Stores.
FanFest hours are from 11 a.m. to 4 p.m. PT each day, with parking available at the Safeco Field garage for $5 in advance or $10 at the door.
Mariners account representatives will also be on hand to let fans try out the different views from seats that will be available in any of the variety of season-ticket packages for the upcoming season.