You know why you want to involve people. You’ve got the go-ahead from the organisation. The people are ready to make the work happen, you’ve got the budget and staff time agreed, and you know the barriers you’re going to face. Now you just have to plan how to do it.
If you have a project-planning framework in your organisation, you might use it to shape your plan. If you don’t, you can pull one together in a way that works for you. The key thing is that the work is thought through and agreed by all the relevant people.