I was thinking along the same lines as Moosmom. You need to start handeling them soon. The longer you wait the worse it will get. You said that they were outside with mom for about 5 weeks so my guess is that she has already instilled the feral fears.
Moosmom shared her wonderful way of handling little scared ferals so I thought I would share with you the way I did mine. I would sit on the floor and play string. I always used a long one so they felt they were a safe distance from me. Sometimes I would tie a feather on the end or a anything that kept their interest. I would throw it , drag it, wiggle it, and slowly drag it closer and closer to me. If they did get close to me the first few times I tried this I did not touch them. They began to be less afraid of being close. After awhile I would reach out and rub their back as they chased the string. I always made sure they weren't looking in the beginning. You may have to force the situation a little. You know...one runs by so you grab it, give quick chin and neck scritchies and let it go.
I would always have treat time with canned food after the playtime. If they bury their faces in canned food you can walk right up and do the lower back above the tail scratch and they love it.
You will know at what pace to move with each one. Moosmom's way sounds easier to me but this is what I did with all mine.
Good luck!
btw/I don't think those kittens could get any cuter!!!!
I hope mama is not pregnant again!!!!!!! Poor you and Mama!