I just went home to Nepal this Dashin, and took one big backpack (fitting 17.2" laptop) and one small carry-on luggange.in plane. I saw other passengers do that same too.
I would suggest you buy a sturdy laptop backpack ( I bought this one : link
and put both laptops in your backpack when going from here. TSA requres you to take out laptops and put in separate bin while scanning). Then when you're in your final transit, you can put one laptop in your carry one luggage (but it doesn't matter, as I mentioned they don't open your bags in kathmandu airport).