Same here. It is really demoralising working for a line manager who is constantly negative about the institution. OP doesn't come across that way though.
This sort of situation is never easy, but with my group I try to:
Ask / know what level of detail different people want on decisions
Ask / know what worries individuals most - job security? Workloads? Career prospects?
With that context, explain decisions with the rationales senior management have offered.
Discuss reservations at group level in terms of how we deal with the issue as a group, report back any constructive suggestions or serious reservations not anticipated from the group to higher management.
Not assume or promote group think. I manage a few units. Often I'm not keen on an idea and one or two of these groups is. I've been surprised more than once. So I never come in first with how I feel about something because that actually doesn't matter very much to anyone.
And just keep it professional and as unemotional as possible - empower people to consider how they'll deal with changes as much as possible.
Not perfect, but I am really not a fan of either extreme of just agreeing it's rubbish and we have no choice, or pretending you're happy with everything.