Same game as Aliens, but with two medics. We found that the smart Aliens quickly ganged up to identify and kill the medics, so the Aliens always won.
Here’s the switch:
When a medic heals a downed human, the healed human becomes the medic in their place. That way, the Aliens have a much tougher time identifying the medics. Be sure the kids understand there can only be two medics at any one time (no cheating!) and that when a medic is killed, their healing capacity dies with them (i.e., even if they are brought back to life, and thus become the new medic, the team is still down to one medic). Sounds complicated, but once they play this variation a few times, they quickly “get it.”
ANOTHER VARIATION to even up the odds with small groups: The Aliens cannot run, only walk.