We Disney "experts" might say that DHS and AK are both 1/2 day parks. But, 1st timers, note that to see all of the shows and attractions, IMHO it may take 2 days at each park or at least park hopper tickets. With little ones, I think it's exhausting to park hop. With teenagers, park hopping is essential. At DHS you must see Beauty and the Beast, Lights, Motor, Action..., Indiana Jones, ride Tower of Terror and Rockin Roller Coaster, Toy Story Midway Mania ( a FP+ must), Star Tours ( sign up for Jedi Training Academy if you have little ones who want to "fight" Darth Vader), schedule in time for character meet n greets, The Great Movie Ride, Backlot Tour, and end the night with a Fantasmic Dinner Package. See the parade mid day if you have little ones. If you like American Idol, then take a break and watch the show ( or even audition if you like). The Voyage of the Little Mermaid is also a show to see. Little ones will enjoy the Disney Jr. show.
So... yes it can be a full day park!