Avajoy,
Sounds like great progress in getting her trust.
Does the Momma cat have a safe place around your
house where she might hide & birth the babies? A shed
or dense bushes, under a porch, etc.? If you make her
secure it her food source (your place), & hope she has
the babies close by, she will not readily leave the area.
You have longer to trap her after the babies are 5-6 wks
old (and the babies too). Just a thought. Maybe you
don't want to wait that long? Good luck to you.