Impress them with your ideas, not the language.
Just 'talk' to them in simple, informal sentences. Many writers fear that they'll be demeaning their topic or their role unless they use formal language and complex sentences. That's wrong.
Research in 2006 showed that if readers have difficulty interpreting the language they rate the message less convincing and the author less intelligent.
Don't use language that would seem pompous in conversation. It makes our readers think we're old-fashioned bureaucrats and people they can't relate to.
You can talk to your readers in formal or technical reports too. As you write, imagine you are in the meeting with the senior management team making the same points. The language won't be quite as informal as you'd use in an email to a client you know well, but still closer to conversation than most reports. It will also be easier to read, absorb and remember.