Are you putting out cages or traps? Sorry, I am a little confused by that.
If you have a live trap, or two, they are much preferable when you are trying to trap a feral cat. You can always transfer the cat to a cage after if that is your inclination.
You said the kittens are three to four months? If that is the case they will be fine if mom is trapped first as long as you are/have been feeding them. The kittens won't go that far away from food. I have caught mom one night, removed her, and then caught two, even three kittens at a time in a live trap within a few hours of trapping mom.
Yes, it takes patience. Lots of patience. Two of my ferals were three years before I caught them. It can be done. Good luck.