You could probably get away with one of em being prot, or at least partly into prot to get the shield throw. Its easier to heal when one character takes all the dmg. And its also easier to gear up one toon to be a bit tougher, i.e. give him the best stuff first, then it goes to the others.

And you can play around with the judgements. 5x light or 5x wisdom might be nice, but I'd be willing to bet that mix and match is more efficient overall. Maybe put one or two each on light/wis, and put the rest into others, like the one that does a stacking DoT (I forget the name)

Man, every time i think of stacking paladins I start loving the idea of stacking auras. Spec one paladin into the improved version of each aura, and roll that way. And I'd give em each the glyph that adds AoE healing. 5x holy lights that also have splash healing will work wonders I bet.