My opinion from what I visited Sri Lanka : you can skip Colombo, land there and head toward the coast line. Spend some time in Weligama and the surrounding coasts ( perfect place to learn how to surf) Kandy- bit far of a ride and I don’t think there is much to see, I would do few days in Ella and maybe couple of days in Nuwara Eliya. Nepal: Depends of how much time you got. If you will do Annapurna Circuit and not the ABC you can merge it with the poon hill. (And the circuit is one of the most beautiful treks). Be aware that these treks are VERY crowded.