The only at-home ant killer that has ever worked for me is Combat. They make a Ant killing GEL that you squirt on the perimeter of the room, but really only where you have seen them. They swarm it! It's amazing. Then by about a week later, they are dead. Sometimes I have had to use several containers of the stuff, but only when there were a ton of ants (when I see they have consumed all of one application, I put another down, etc, until I don't see them anymore). FYI - the only place I have found that actually sells the gel, is Home Depot.
You certainly wouldn't want you kids or pets playing with it directly, but if you apply it when the 2 year old is napping of something, they really shouldn't even notice that it is there.
Good luck!