As I said before, usually the only things that will create a conflict is where two people try to modify the same part of the project at the same time. It's explained more in this tutorial.
I'd recommend a workflow where people have clear roles to try to avoid conflicts. For example your proposed workflow does not guarantee that, as "add interactivity" could include a wide range of potentially conflicting changes, e.g. two people could modify the same event block in the same event sheet and still cause a conflict. However if two people are working on separate layouts or separate event sheets, that should avoid a conflict.
Remember even if you do get a conflict, it can be resolved, but it can be tricky - the easiest way is just to roll back and try again. Over time you should get a feel for what kinds of changes are safe and which risk conflicting with your team members, depending on who is working on what.