That should be fine, as it's not a large quantity and therefore probably won't give them diarrhea (some cats react that way to liver). While they shouldn't be fed too much liver, a little bit now and then is okay - many cat foods also contain it.
I see they've already decided for you, but wanted to add for anyone else reading this threat, in addition to what Tricia said, you'd want to be sure not to give them the chicken liver if you were using onion in your cooking water.
Onions in any form are toxic for cats and can cause Heinz Body Anemia.
Mine love chicken liver, I buy it as a treat, though it is a bit rich if they eat too much. Some cats like to have it whole, and if you can bear it, will 'hunt' it over the kitchen floor before they eat it, others insist on having it all minced up like cat food.