There are six armies. Three of us. So there'll be a chance to use each one, or to concentrate on using one or two. We'll make it up on the day.
Imperium of Man:
2nd regt infantry force with fire support
Valhallans - pure infantry
Bel Tain - shooty Eldar scouting force
Dark Eldar - hover skif mounted raiding force with close combat HQ element
99th regt (Bloodcoats) infantry force with a modicum of fire support and workers rabble
13th regt (Tigers) infantry force with two sentinals and a mutant rabble
These are only 400 point armies (about 50 bodies) and really we're just doing this to learn the rules. There isn't much room for tactical shenanigans beyond the obvious.