Until you start doing dungeons, ret is perfect for your paladin. The mage, frost is more of a "keep them contained" spec, which might be wasted when paired with a paladin. I would go either Arcane or Fire, or a combo of both. Fire has a nice range, which helps sometimes. I leveled my mages all fire, and respecced (free with 3.0 patch) to Arcane. I think I did more overall damage as fire, but as arcane, I do pretty well with mana, and much better AoE (with Arcane Explosion)

I think you picked a very good combo. Enjoy it! Also, make sure you get all 3 gathering professions, its much easier to level up and gether, and worry about crafting later. Put skinning on the mage, as its possible to macro skinning on an alt, where mining and herbing have to be clicked. I'd also consider enchanting, as it makes green and blue drops that you can't use useful for income.