I feel the same way you do - I want my guests to enjoy their privacy, but I also want them to know that I am accessible. I greet them personally when they arrive, and am sensitive to whether or not they are the sort who would like to engage with me for a bit, or are anxious for me to show them around and then be on my way. No matter how long, or how short, our intitial interaction has been, I then send a text message late morning after their first night saying something like, "Just checking in with you to make sure that you are comfortable, and that everything is meeting your expectations. Do you have any questions, or is there anything I can do to make your stay more pleasant?"
To me, a text is friendly but not intrusive. And I always wait until late morning, on the chance they wish to sleep in! I understand that some guests might be hesitant to ask questions or to make comments, so I want to be the first one to extend that invitation.
I also send a text message the night before they are scheduled to leave, confirming their departure time and my check-out procedures.
Jude