In most states, it is illegal to harm or exterminate bats. The most effective and humane way to get rid of bats is with a one way valve (bat cone or bat valve). The bat cone allows a bat to safely leave your attic but it prevents reentry. Seal all potential entry points before installing a bat cone.
Finally, you cannot start bat exclusion if flightless pups are present in your attic. The pups are completely dependant on their mothers. Abandonded pups in your attic will die.