That should be fine to run 5 accounts on. There are numerous sticky threads in these forums with instructions on that. I recommend picking a single class for all 5 of your characters on your first attempt at multi-boxing so that you can use all of the same spells & hotkeys across the accounts. It cuts down on the need to multi-task significantly.

Many people choose shaman for this because in elemental spec they do excellent ranged damage, yet can still heal, and many of their totem buffs are additive, so you 5x the benefits of some of the buffs. They are also not nearly as squishy as the cloth DPS classes.