Mother cat on antibiotics, now kittens have diarrhea?

About 7 days ago my momma cat hurt her back leg and our vet placed her on amoxi. Her leg is healing well but now her kittens have diarrhea. They are just over 4 weeks old but are rather small as they were born roughly 5 days early. Still playing normally, no sneezing or coughing. Just loose pale stools. Other than calling the vet (going to Monday) any ideas as to what I can do for them?

Some probiotic is never wrong for mom nor the kittens.

You may use human probiotic too, to perhaps sprinkle on their food. Doesnt need to be made especially for cats.

The easiest is to use some plain unsweetened youghurt.  If it has added some of these healthy bacterias, its even better. (acidophilus and bacillophilus (spellings?) the most common)

Is there a dosage chart I can find? The largest kitten is just under 12 ounces. They've reached 5 weeks old today.

dosages?  I myself dont know.  It is no huge amounts. With such small kittens it is a few ml.=  a  mouthfull, not more.   But you will surely find more about it if you seek.  I know there were threads in the Nutrition forum.

What they dont eat up, you can yourself eat up, its also good human food.  

Great, thank you very much StefanZ. Their stool seems to be firming up a bit, and I've offered them some softened kitten food to them as well. Two will eat it (the largest two) and the others look at me like I'm crazy . So far so good.

You should be worming both mum and kittens against roundworms, both now, and in 3 & 6 weeks time.  These are very sneaky worms which will encyst in the mother's body.  When encysted a wormer won't kill them.  The hormonal changes of pregnancy wake them up and they migrate to the kittens in her milk.  So, ideally a pregnant cat would also be wormed a couple of weeks before her expected date of delivery.  In the UK we would use Milbemax for the mother, and Panacur for the kittens at first, then Milbemax once they are at least 6 weeks old and 1kg (I think) in weight.  Personally I find a small tablet like Milbemax much easier to give than the liquid Panacur.  I've not tried the paste Panacur.

Kittens and mum have been wormed. The smallest kitten is now 1lb and all four are eating well (and diarrhea free) . Thanks everyone for your help.