Update: Last Thursday evening, I sprinkled Sluggo around the raised bed where the sunflowers are and have had no bites since then! One of the original 5 remains unscathed; two said their goodbyes due to the slugs, one has moderate damage that seems to be fine, and one had a LOT of damage but miraculously is growing new leaves.
Happy to say that so far, so good! Sluggo appears to have done the trick.
