Solil, not long now!
And there should be no question about them leaving on Sunday. If there is any doubt at all then your husband must speak to them again. Don't leave it vague or open, make sure everyone knows that on Sunday it's time to go home.
You could ask things like "what time are you making a move on Sunday? Did you want some food to take with you for the journey?" Or "please don't feel rushed, but Sunday afternoon hubby me and the kids have been invited to a friends house, were you hoping to get going in the morning?"
Make sure your husband is there at the time, and is willing to counter any descent such as "oh we're not sure when we'll be off". Practice your strategy if needs be, and approach the situation as a strong team (you and hubby together).
Whatever words you use, however clumsy they come out, the result must be that they leave on Sunday.
May the Fools Force be with you!