It is very IMPORTANT for parents to have alone time to be a couple and get to know each other in a private setting where they have real time to reconnect. I have babysat for my kids on various occasions.
NEVER, EVER leave your children without telling them. THEY don’t like surprises. It terrifies them.
What we do is tell the kids, “your so lucky you are going to have a sleep-over with Bubby and Zaidy. You are so lucky, how much fun is that going to be? Just you and them?” and then after they get excited about that, tell them Mommy and Daddy are going to go away for a few days while you and Bubby are going to have your sleep-over.
Usually what happens is that when the parents come to pick them up they don’t want to go home.