Ermmm...I notice you have Knowledge Devotion as a first level feat. How is this possible when the prereq asks for 5 ranks in a Knowledge skill? Shouldn't you only have had 4 ranks at level 1?
Anyway, on topic. It's basically you(cleric) and a Psion Spy vs a Paladin and a Rouge without UMD? Why would you even NEED a plan? Just toss all your damaging spells at the Rouge and wear the paladin down. You might want to actually start NEXT to the Paladin so he can't Mounted charge you(assuming he is even capable of that).
Anyway, if the paladins got heavy armor, creative use of 'Make Whole' might let you fuse his armor's plates together(making the seperate pieces of armor into 1 'whole'). Completely negating him in 1 turn without a need to bypass those pesky paladin saves.
If your brother wont allow shenanigans, just buy a few Holy arrows and some sovereign glue. At the first sign of trouble tell them tell them to grab the arrows quick, dont ask question you'll need them do it now. It sticks to their hands giving them a negative level. 6 arrows each should kill them then for extra funsies just command the resulting wights. Of course, this works better if they dont know those arrows are Holy(tell them they are eager warning arrows or something)