Unless your Bichons eat a huge quantity of the ant bait and every day for a year, they should be fine.
Abamectin is similar to ivermectin, the active ingredient in Heartgard. It has a wide safety range.
I'd just keep an eye open for any vomiting or diarrhea, lethargy, or tremors. But I think they will be just fine if they come in contact with, and snack on, a couple deceased cockroaches.
I hope this helps!!