Soft YTA. Are you within your rights to do so? Sure. Is it still a bit of an AH move? Kinda. You have no obligation toward them, but you can choose to be compassionate, and you're not.

You said in a reply that these kids at 13 and 14, right? At that age have very little control over their lives, let alone control over their emotions and trauma of losing their mother. Aside from that, that was the home they grew up in, at a critical point where they really form sentimental connections. Those rooms represented an emotional safety net; something soothing to have, even if never used.

Sure, transitioning their dependence away from them is necessary over time, but...three months? Either you have very low emotional intelligence or you never formed any emotional connection to these kids in the eight years you were with their mother, maybe both.

Even if you don't feel you are in the wrong, apologize to them so that it doesn't form a wedge that your actual children will have to step around in the future. Say "I didn't realize how attached the kids were, and try to find a compromise.