16 month old twins -eating habits?

My babies were born at 33 wks. I�m a full time working mother who hasn�t had a break for the last 16mths. My babies have just begun to walk and I�ve already tried giving them normal food...they just play with it or choke and vomit(especially if they�ve just had soup or pur�). One of them is an expert at vomiting. What is the best way to go about introducing normal food? I�ve tried teaching them how to chew but they never use their teeth to do it (just the tongue and the roof of their mouths instead). Otherwise they are developing normally. Does anyone have any tips or food recipes for 16 mth olds?