All three of them should play, also Mahela should open in every match with Dilshan.
Mahela should be SL open batsmna for all limited overs cricket
ODI all 3 should be there.
but T20 only dilshan.
T20 important things big hitting and all rounder skills.
dilshan is all rounder and can do big hitting.
but other 2 r specialist batsmen.
mahela form is out and sanga strike rate is low in recent years.
Dilshan and Kusal r best 4 openers.