Best way to begin introducing separate bedrooms?

We are the POA and primary caregivers for my husband's parents, who live with us in their own suite. Dad's dementia has progressed to early stage 6. He struggles to shower and change clothes, often going to bed with coins in his pockets. Mom's dementia is progressing faster, but she is not nearly as impacted so far and was diagnosed a year ago. She is at a point where learning to treat Dad more kindly because his behaviors are based in the disease is really not possible in any sustained manner.

Our plan is to move to two twin beds in their bedroom and set up a 2nd bedroom with another bed so Mom has a place to go in the middle of the night. They've been married >60yrs. While Mom is beginning to feel like she needs that separate space, we know this will be hard.

So, has anyone done something like this where they've successfully separated a married couple into separate rooms? What are your lessons learned and areas we should pay extra attention to?