Child’s bedroom on the ground floor away from parents?

TLDR: I want to move my son to our office to give him his own room, husband has concerns

Our house is a 1970s bi-level. The kitchen, dining, and living rooms are on the second floor, along with three bedrooms and a bathroom. The ground floor has a bedroom, laundry room, family room (which is the kids’ playroom), and an office that is actually suitable for a bedroom (has a window and a closet).

My mother in law lives with us and has the downstairs bedroom. Right now, my twin 5.5 year olds share one upstairs room, my 6.5 year old has the other, and we have the third.

Lately, one of my twins has really been wanting his own space from his brother. Their current room is too small to split in any reasonable way, and there’s only one window so if we split structurally, one room wouldn’t have egress. “Soft” splits like curtains/dividers won’t be enough separation.

My idea is to give him the office as a bedroom. It’s a decent size room for a kid, and would easily fit his furniture with some room to keep his toys. It’s right off the playroom and on the same level as his grandmother’s room.

My husband is uncomfortable because we would be on a different floor, and also because there is a large window that faces the front of the house. He wouldn’t be alone on that floor, as my mother-in-law’s bedroom is also down there. There’s a full bathroom, so he wouldn’t need to manage stairs to go to the bathroom at night. And as far as the window goes, we live in a very safe and quiet area. I figured we would put 2-way film, a window alarm, and a camera with a motion light outside his window as added security.

Am I crazy for thinking that this is a perfectly fine solution to our bedroom problem? I know it’s not ideal for him to be on a separate floor from us and his siblings, but it seems like the best option that we have.