questions about kittens

i have a question about the three kittens that my mom just got from my grandmothers backyard. they are stray kittens and we try to take them to our local shelter but since they were closed we kept them home and took care of them for the whole weekend. the next time we wind up calling numerous shelters and hey are all saying the same thing that their full but they want donations. i called the  aspca but they told me they only investigate animal cruelty. i cant afford to take care of them plus i have guard dog that is not friendly to any new pets that comes along, so the question i wanted to ask since no one else cares about animals, would it be a good idea to give the kittens back to the mother?

please everybody let me know what i should do because even though im not that much of a cat person i  dont want absolutley nobody to hurt these kittens they deserve a home and healthy and safe lifestyle.

@ scaredy cat
thank you so much for the sources that you gave me
sorry that i was of topic but in a way im in a panic a little bit because it seems like nobody cares not even so called "rescue"shelters. and to think they are acually little newborn kittens imagine what happens to older stray animals.
anyway thanks so much i appreciate it.

oops its 8 weeks old when they should be weened

If we lived in the same City - I could give you resources but I think each City has their own 'heaven can wait' type shelters.
Heck - I have 3 cats of my own but I would even take them if it was between that or putting them down ...I just can't handle that idea.