To understand the Aeneid's take on the theme of mortality, its useful to compare its view with that of the epic poems of Homer, from which Virgil took so many of his ideas. In Homer's Iliad and Odyssey, the central idea is that the underworld stinks. This crummy future that everyone has to look forward to just makes Homer's characters all the more determined to live it up while they're here – which usually involves killing lots of other guys and winning great glory. What makes the Aeneid different is its emphasis on the idea of reincarnation. Basically, if you have a chance of being reborn (and Book 6 kind of makes it seem like everyone – except for the worst of the worst – will be, after enough millennia of punishment), then death doesn't have the aura of grim finality as it does in Homer. Just think of the fact that the descent to the underworld comes in Book 6, smack dab in the middle of the poem. Before it, Aeneas is kind of depressed, but afterward (after seeing how cool the future of Rome will be) he's all excited about his mission. That's kind of what death is like in this poem: a way-station on your way to better things. This view of death makes characters more interested in being good in ways we would recognize, like being pious, and good to your family, instead of simply being the best warrior.
Despite Anchises's depiction of the soul as contaminated by the body in Book 6, the Aeneid portrays the life on earth as more important than life after death.
The Aeneid depicts the death of a son as the worst thing that can happen.