i think its ok if its a walk out basement in the back. having a wall of glass on one side would take the onus off of "the best bedroom" being downstairs.

but really this only matters to you. if you are good with the idea thats fine. the next owner will do what they want with the space.

i would say when its time to sell, move the master back upstairs and shift the kiddos around. i think a lot of people wouldnt see beyond the master bedroom being in the basement.

I did a reno where I put the master suite in the walk out basement of a home and it was awesome, the owners could walk out to the hot tub from there and we installed a cappuccino machine so they could have morning coffee outside I think if it is done well it could actually be a selling point. It is usually quiet in the basement theonly thing is make it is a suite with a fabulous bathroom too.

Below grade space doesn't have a similar appraisal value to above grade space. And there are health and safety codes that apply to bedrooms underground that would not apply to other forms of living spaces. Such as emergency escape and egress and arc fault outlets. Creating a master underground may be more expensive than you anticipate, and give you far less return than you would think. But if you solve those issues, and you are OK leaving the children all alone on the ground floor, then you may get enough use out of it to make the economic expense of the project justify itself.

not only is it quiet, but if you suffer from heat it is easier to cool. warmer in winter too