Maybe it's not fear....maybe they don't taste good, like if they weren't fed on decent food prior to offering. I would try keeping the crickets for a few days or a week & feeding well before offering....see if that makes a difference. (I think crickets will eat most anything, & if you're offering them straight from the pet
store, maybe they aren't feeding them quality food. They might be eating newspaper for all you know?)
If I'm not mistaken, don't cresties also like Dubia roaches? That's another option...