I've been reading a lot of Hobbit fic and it strikes me that I've not seen fic where Thorin (Dis, their people, etc) sees the possible loss of Fili and Kili as a loss the royal family is simply required to bear. In other words, the obligation of the royal family to its people.
I find Tolkien's love of noble people who are simply better than the rest of us problematic in lots of ways, but it is part and parcel of his world and a large part of the mythologies, legends, and histories he was drawing upon. The obligations of the ruler to the ruled are explicit in this ideal world and I can't see how Thorin would even think to himself that his heirs wouldn't participate.
Thorin's storyline involves a lot of lust after material possessions, but it springs out of a noble desire to fulfill his duty to his people, to provide for them and by returning them to their home. And that duty belongs to Fili and Kili, too. I think Thorin and Dis are very aware this may end in death and that they both were raised to believe that their lives and that of their children belong to their people. But the overwhelming trend in fics that I see is Thorin and/or Dis acting more like modern parents, afraid of losing the boys, angsting over their involvement. It just doesn't fit how I see Tolkien's warrior kings of old.
So, of course, the exception that proves the rule
Sons of Durin by Inklinghttp://archiveofourown.org/works/595550