I'm sure there won't be a problem as long as you include the yorkie into the babies life. When I bought by son home ( 25yrs ago next month) I put him on the floor and let my dogs smell and lick him. They loved and protected him till the day they died. My yorkies love babies, pity the people I know with babies have a fit when Coco tries to smell and lick their hands
Congratulations on your new additions!
Sheilagh