Just put the food in their bowls & leave it down for them to eat. They will eat when they are hungry enough. A dog will not starve itself if there is food available. They will eat out of the bowls when hungry enough. They may not like the food you are buying. If you switch foods, take about a couple of weeks in changing from one to another, gradually adding more of the new & less of the old but take the time to do a proper switch or the dogs will get diarrhea from a sudden switch.
Rubbish......If the dogs are hungry enough they WILL eat out of anything including another dogs bowl.
Don`t feed them ANYHING, not even a treat, for 1-2 days + and then watch them eat out of their bowls. NO healthy dog is going to deliberately starve itself to death, just because its food is in a bowl.