Garfield's Scary Scavenger Hunt is a exploratory activity in which kids can navigate Garfield around a haunted house to find his favorite snacks. Though not as dense as, say Myst, it could take some time, and I didn't actually finish it. Kids would have great fun encountering the "scares" and moving about the house, solving problems such as locked doors and other obstacles. You can keep track of the screens on which items were located (# in upper left corner) and go back to them quickly if you were to break the task over several sessions.
Spatial concepts would be a great target as you navigate; the activity is also a logical context for conditionals and the categories of snack foods, scary sights and rooms of a house.
Thanks to InTec Insights for highlighting this resource. Also see Karen Ogen's great post on interactive Autumn games, many of them language-based.