Why should a WO need to go to 2 groups? If there are 2 tasks to be done the person managing the whole change should set up another WO for the other WG's task.
Generally when managing a change you will either know exactly how it should go and who should do what - in which case it is a standard (ITIL terminology) change and you can set it all up as in a template, or the person responsible for the change will have to decide what WOs for what groups are required and set these up.
Using this approach means that the person managing the change can see how each step s going and each group doing a task focusses on their own work order.
We have linked different work orders as per the change flow(e.g impact assessment,implementation etc) within a change. If the impact assessment for a change request has to be done by 2 different teams, then are you saying that the Change manager should create an additional work order & assign it to the other workgroup ?