S.H.
All you have to do: is ASK them WHAT THEIR PLANS ARE... because you/Husband have to PLAN AHEAD. You all have your own schedules too and obligations.
You simply, ASK them.
AHEAD of time.
Tell them you need a clear and defined, answer.
AND you clearly, lay out and tell them, how long they can stay, according to you and Hubby.
It is your home, you decide how long they can stay.