We would definitely recommend the stay in Sandra's house within her family. She is a very warm-hearted person and from the very beginning you feel welcome.
We had a nice clean room with a beautiful view over a river and shared the bathroom with the family, which was never a problem.
Every day started with a delicious breakfast from Sandra (at any time we wanted) and an exited conversation about what we've done the day before and what to see in Rotterdam. You could ask her everything.
Her house can be found easily and the metro station is only a few minutes walk away, even though the metro does not run that frequently as you are maybe used to it.
All in all we had a great stay in Rotterdam, because of the very friendly people living there and Sandra completed this impression.
Thank you Sandra and all the best for you and your family.