I had a similar situation myself. Had a setting momma and chicks hatching in the 'bator. I didn't want to raise the babies myself so I gave them to momma. I took the babies out to the coop at dusk. Tossed mom off the nest to eat and drink and then put the babies in the nest. When she came back in she hopped up into the nest and saw the babies. She really looked confused but settled over the chicks and tucked her one egg under her. I watched for awhile and there were no problems. She ended up raising them without any problems.