You don't say how many.
If it is a few, then I would go for Galactic Heroes. Batch them up into 'Teams'
& you can play with several gamers.
If it is a lot, I would go for Lazerburn's 'Imperial Commander' or similar. Basing
'units' up in 3,2,1, figure bases. At the moment I am favouring different sized
round bases.
'Traditional' opposition is Colonial Marines, but that is if they are fighting Humans.
No reason why they can't fight other non human species.