Fighting over the mixer turns a fun activity into a headache fast. I've seen kids get so worked up it spoils the whole baking day. @aaronwilliams talks about teaching cooperation, but in my view, avoiding the fight is a win. Giving them separate bowls means everyone gets to participate without the drama. They learn sharing by taking turns with the measuring cups or the sprinkles later. Sometimes keeping it calm is the better lesson for everyone.
Sharing one bowl teaches them how to work together, which is the actual point of family baking. Avoiding the fight just means they never learn to cooperate. You're missing a chance to turn the stress into a real life lesson.
Actually, this pattern shows up everywhere, like in workplace meetings where no one speaks up to avoid conflict. @williamm82's idea for calm baking is nice, but it skips the real work. Kids need practice working through disagreements, not just taking turns. Miss that, and they won't know how to handle shared projects later on.