I think you are ok to play them versus the preset Warlock. You get many +s from the idols, whereas he has two creatures total that can. The bats die in a stiff breeze and even if the bats gets both +1 charge and +1 pierce, you are looking at two 0 armor, 4 health, 3 attack dice, 1 pierce rot generators.
To counter those juggernaut bats you have retaliate, geysers (probably better holding for anti-burn duty), jet stream (a death sentence for a bat usually), block, fast moving falcons, eagle wings on very hard to hit Sosruko etc.
Use the idols, you'll get far more out of it than he will and you'll have far larger threats to handle versus the warlock than the two bats. My opinion, anyways.