Nah, you don't want a floor drain in a garage. Too many issues with that.
Hot water won't stop all buildup of grease in drains that they live on, even with daily use.
I wouldn't bother with an insecticide, and you really don't want to be exposing yourself or children to unnecessary pesticides, right?
Remove the food source, and they will be gone very fast. An enzyme drain cleaner is perfectly safe to use, and a quart size container will last you years for this purpose.