then how to educate our muslim brothers and sisters regarding this "vaastu saastra" or "feng shui" issue
Are you the thread starter ?
If you want to give our Muslim brother and sister an Islamic architectural guidelines that similar with "vaastu saastra" or "feng shui", I doubt you can find Islamic architectural guidelines like this.
I am not familiar with "vaastu saastra". But "feng shui" is a guideline to make a harmony between building and nature. "Feng shui" concept is configure the building for invite or increase good energy, and prevent or decrease bad energy. I think "vaastu saastra" is not so different than "feng shui". And actually concept like this is based on polytheism.
How to educate our Muslim brother and sister ?. Remind them about shirk.
As I said, I am not familiar with "vaastu saastra". But I see, in Islamic perspective, "feng shui" is really shirk. In example, if you make a bedroom in this side and kitchen in that side, good luck would comes to you. If your main door facing to wrong side, bad luck would always comes to you. Or if your house is near something your family would always in illness, and if you want your family have a good health you must make a fish pond in this corner. And many more.
Brother Zakirs told me, Indian Muslim people use "vaastu saastra" as a guideline because they expect they can sell or rent their houses to Hindus people. I think in case like this we can make a little compromise, co-working with Hindu architect. Let them make a basic design that according to "vaastu saastra". We cannot participate in this stage because we must avoid shirk. But we can take over finishing stage, add this basic design with artistic touch.
However, if we make a building only for us, I mean not for sale or rent, it's better if we use 'neutral' architectural guidelines such as, how to build a healthy house, how to build a green house, etc.
PS : My advice probably controversial. I hope someone can make a comment for it.