yes, I take your point about child safety.
Scattering them thinly, rather than putting them in piles, makes them less likely to be eaten by non-molluscs, as does putting them out of sight in cracks, crevices and under things such as pots and bushes. I have heard, though, that a human could eat a kg of slug pellets without ill-effects, it is more of a concern with small birds that might be attracted to a pile of pellets, or a child eating them out of the container. Spreading them over a wide area makes it more likely that a slug will come across one as it gallops about.
If the slugs are getting in under the door, try sweeping pellets towards the doorstep so they are in the angle, also you can put them under kitchen units, skirting boards, down any holes in the floor where pipes come up. brushing them around a path will also encourage them into cracks.
The slugs are probably living in some damp shady area, perhaps in the garden or an ivy-covered wall, unless you have damp under the floor or behind the sink from a cracked drain or pipe, so try pelleting there. It does take a couple of weeks to get the population down, as slugs are more itinerant than you'd think. Once you've got rid of most of them, you can concentrate the treatment on the "borders" to catch the new ones coming in.
If you put pellets out in the evening, the slugs will tend to eat them overnight. They break down when rained on.
You can also look in garden centres for a liquid slug killer that you mix with water and sprinkle onto leafy plants that the slugs eat. Last time I got some it was Murphys Slugit in a small white bottle.