Customizing Keep on the Shadowfell for two player characters

[Abisashi]

Allow each player to choose a class template from the DMG; this should allow them to better cover the four roles and make them more versatile and durable. I'd also bump them up a level, maybe two.

Edit: Also, they should get an action point every encounter.

 

[Pseudopsyche]

i would try both starting your PCs at a higher level and then removing monsters from encounters to fit your encounter budget. For a while I ran KotS for three 3rd-level PCs (without modifying the encounters), and it worked pretty well. For only two 3rd-level PCs, you would need to scale a 500-XP encounter to 300 XP (to preserve the same relative challenge).