Check what they drink, and if needs be, get in some decaf tea/coffee, sweeteners, juice, etc.
Check for any food allergies, intolerances, dislikes.
I wouldn’t leave bottles of water or food in the rooms, just let people know where to get water, tea, cheese, whatever.
Make sure the heating is on in the bedrooms, but tell/show them how to turn off the radiator if it’s too warm for them.
Leave out a bath towel, hand towel and face cloth for each guest.
Agree re toilet flushing (or not) in the night.
If you have an alarm, show them how to turn it off if they’re up first.
If we have friends with children visiting, I download a few family films, and some shorter programs for pre-bedtime winding down.
Relax. A chilled host really puts guests at ease.
You’ll be a grand host, I’m sure.