While some of my peers believe age shouldn't be a factor, alas, it is.
Experienced people who have been at the company for many years, can feel cheated or worse when there's a new boss and that person is a) relatively speaking, a kid, and b) has no experience in the company.
Putting a younger person above a productive older employee can be felt as a loss of a promotion and the end of hope for future recognition. It can also be felt as a put-down of what the experienced employee has learned and is able to contribute which includes wisdom, relationships, perspective, knowledge and leadership.
That can be damn hard to take.
Fortunately, I once had the experience of babysitting my two grandchildren. The kids wanted me to put on a movie. Now, my son had created a complex entertainment system and I couldn't work it. Frustrated, 2 1/2 year old Josh marched up to me, pulled the remote control, and impatiently started punching buttons. And he got it to work!
In that moment, I realized I would never be as comfortable with IT as these two. I would be seeking their help and not the reverse. That's the fact I had to get used to.
If the executive candidate has the cultural fit and exceptional technical skills, I would introduce the candidate to the impacted group where each person introduced themselves and their role. Last of all, the candidate.
I would talk about what the new executive was expected to add to our group and ask each person to engage in conversation with the newcomer, especially about our values, expectations, and unsaid rules. I'd close with hope that things would work out well.
After the meeting, I would seek out individuals likely to have difficulty accepting the young outsider and give them a 1-on-1 opportunity to vent, problem solve, and maybe volunteer to be a mentor. It would also be great if there were new opportunities to learn and lead that could be offered. That would not be as great as a promotion, but could still be a heady form of recognition.