You want the two characters to shine, and the third to be mostly a sidekick. While a Paladin is a great addition to the party, I don't think they make very good sidekicks. I'd go with a sword and broad Fighter, probably human, maybe with Initiate of the Faith.
Another option is to forget regular classes, and just make an NPC. It would be much easier to give him a few abilities you think the players will need, without worrying about a "legal" character. Fewer abilities (and no dailies or action points) will make it faster to run. It's not easy to run a full blown character and be a DM at the same time. Any activation time you spend on that character, is time you're taking away from the two players.
Another option is to forget regular classes, and just make an NPC. It would be much easier to give him a few abilities you think the players will need, without worrying about a "legal" character. Fewer abilities (and no dailies or action points) will make it faster to run. It's not easy to run a full blown character and be a DM at the same time. Any activation time you spend on that character, is time you're taking away from the two players.