If everyone is going to be new to 4e, I'd say either stick with the 4 iconic classes (Fighter, Rogue, Cleric, Wizard) or stick with the four Martial power classes (Fighter, Rogue, Ranger, Warlord). The first group because it's a good way to know you (as DM) have your bases covered as far as party requirements, the second group because it's easier for players to understand conceptually what their group is (they are all warrior types, and don't have to try and wrap their heads around being magic-users or praying to the gods for their abilities).
If you need even a smaller number of recommended classes, I'd say Fighter and Rogue. They both are good in melee combat, and they both are easy to understand from a conceptual point-of-view (the big armored guy with the sword and shield, and the faster swashbuckler with the small blade).
Hope that helps.