Demanding children apologize has a couple big problems. First it sets you up for a power struggle since your children are ultimately in control of what they say. Secondly, forcing kids to say "I’m sorry" when they’re not teaches them to say what other people want to hear even if it’s not the truth.
A better approach is to help your children see the impact of their behavior on others and find a way to make amends. For example, "When you grabbed the shovel from Sam, he started crying. He looks really sad. What do you think you could do to help Sam feel better?" Asking questions helps your children do more of the thinking and learning from situations.
