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Good for you to try and help a new mother with her babies!
Generally, a kitten 1 1/2 weeks old should be fed every 2-4 hours by the mom. If they seem to be sleeping a lot, then it means that mom is feeding them sufficiently. Usually, mom is able to figure out how to keep them warm enough and fed enough on her own. Giving mom food is a good way to help, that way she doesn't need to forage too far or wide to keep as well nourished as possible. I would not recommend moving the kittens since mom seems comfortable with the current location. If it seems like mom doesn't come back for more than 6 hours, then you may need to supplement with kitten milk replacer. It sounds like things are going ok at this point however.
Good luck and I hope this helps.