Mom has mild dementia. Mom is 83 in need of a hip replacement when they relocate to new apt. The new apt will be above my brothers house garage. Dad is 85 in good health. they both know about the move but mom doesnt remember.Mom hasn't seen the apt yet until the new chairlift is installed shortly. I want mom to transition smoothly into the new surroundings. they will be surrounded by her son, daughter in law and grandchildren on a daily basis.
Assisted living sounds like what they need.
As for a party or gathering of friends or family when they move in, that may not be the best idea either as it may overwhelm Mom.
The suggestion to have the new place set up as close to her old home is excellent. I work as a senior move manager and my crew always take photos of the home we are moving out of and then try our best to set up the new place very similar to the old place. Even little nicknacks.
Would it work to let one of the grand kids have the over garage apartment and let Mom and Dad have their room in the main house? Then no expense to add the stair lift and I would guess a very happy grand kid. If they are old enough.
I had an apartment at home when I was growing up and it was super.
I would also go through the apt and look for things that might be an issue as the dementia progresses. That progression can go rapidly or slowly, but I would check things out with the idea that she could be operating with a very different mental state in the near future.
If you want to make the place comfortable, just use their same furniture and hang pictures of the family. You might have a small family housewarming to welcome them and wish them well.
I'd make sure that people who used to visit still visit, but once again, are friends their age going to have access to an upstairs apt? Can they use the chairlift? I'm not sure what it looks like, but I'd make sure it's safe and others feel comfortable using it. You dad is in good health, but still at 80, I'd hesitate to want my dad going up and down stairs multiple times per day. The exercise might be good, but I would fear he might lose his balance, fall and break something.
Being around family members can be very comforting, but it is different. I hope it works out for you all.