Go for it!
Even if some get away, it'll make them think twice about swarming us.
If Rick Levitates himself, can't anyone fast just pull him along weightlessly?
Speaking of one at a time, it might not be a long-term solution, but if I can pick one off or wound it, it won't impact my ability to high-tail it out of there on your signal, and if it prevents one weird compulsion/confusion/fear attack, it'll be worth it.
And anyway, if Isaint, Al, Rick, Yukika, her Spirit, the hellhound, Ethereal, Tamsyn, etc. heck, even Robyn with her whip on a small one, all take out one at a time, it won't really take long to kill them all....there are actually almost as many of us as them, and most of us magical....
But I still like your grenade plan best!!!