Wishing you so much luck with trapping mom cat. That is the way to do it. Let her go in and out to eat for a few days. When you are ready make sure you do NOT let up on that rope. If she gets out before you can latch the door, you will have to go to another method of trapping. Crate and rope trapping is very traumatic because the crate has to be pulled and bounced around till it gets to you. It can be done, I have done it this way before I owned my own trap. Also, just be very, very patient with the kittens, they will learn to trust you slowly and things will progress ever so slightly as the days go on.