Calico cat family stray am taking them?

how hard is it to get them to come home with me mom cat gave birth three weeks ago they live in my cousins back yard their house is close to ours what should i do to get them to trust me here is what i did two days ago i saw her for the first time i gave her tuna fish she ate it but not while am around and she let me get close to her about two inches that is it,, today i went againe i gave her checkin she ate it in front of me but this time i had to stay back she wouldn't let me and i put a box their covered with a balncket and their is two toys a rubber ball and a mikey mouse in it and i also put some water not in the box so what should i do next i think next time am giving her checkin liver is it ok