Well, the kids complained among each other and - despite having agreed upfront to play together, not against each other - started clicking the button to change allies. I fully understand that most people would rightfully argue that this is normal and that kids need to learn, and I totally agree. However, I admittedly was a bit annoyed about it and then thought how nice it would be to have such an option. Now you see the background of my question. Whether it helps to understand it, I don't know, but I fully understand if this is nothing anyone would invest time in.
In case somebody sees other and better reasons to have such an option, feel free to add your thoughts here.