Hi Jen!!
Luckily, at 5 weeks, feral kittens should come around pretty quickly. I'm not even fostering, but I have noticed dramatic changes in the feral kittens at the shelter where I'm volunteering. I spend a few minutes each day handling them, and they're getting so much better about human contact. They are more scared than anything, but I just grab them by the scruff of the neck (if they are really mean, you may want to use gloves or a towel), then hold them securely against me and talk in a soothing voice and pet them. I do this with each kitten, then I put them back in their cages, give them some treats and let them have a break for awhile. Given that there are other cats in your household, and they will be with you at your home, I have no doubt that they will come around pretty quickly! Good luck and enjoy the kittens!
**hugs**
Karen