to be able to treat the problem you need to find where they are coming from...
possibly under doors, or any cables going to the outside of your house?
LO hasnt dropped food or hidden anything anywhere thats attracting them? - the toy box? behind tv unit etc?
put ant powder down where you see the most of them, make sure LO cant eat it...
ie put it down in the morning, go out for the day & then hoover it up before letting LO back down to play..
xx