when you are looking at homes try and look at them through your mums eyes - things that are important to us may not be important to her - and try and look to the the future. Many care homes (even the ones that say they specialise in dementia care) only want the early, easy stages of dementia and once the dementia advances they give notice.
My mum was in a dementia unit (not a nursing home) for three years untill she passed away there. My OH is now in respite in a residential (mixed dementia and non-dementia) and the difference between the twp homes is very obvious.
The place that OH is in has a very "hotel" feel - lovely decor, a library, dining room kitted out like a restaurant, he can walk down to the paper shop down the road to buy a newspaper and it suits him very well at the moment, but would not be a good place for permanent placement. OH has unusual symptoms; he has lost the ability to perform most tasks and is beginning to need help with personal care, his language is dwindling, he has an indwelling catheter and his mobility is going, so that he now requires a zimmer frame to walk. He is unaware of the extent of his limitations and insists that he he is still able to do things. He does not have problems with his short-term memory, though - it is his long-term memory that has problems and the further back you go the worse it gets - but as his short term memory is OK he does not get confused about where and when he is, does not go out and get lost and does not repeat himself.
The home he is in is best suited for the elderly frail with only very early short-term memory loss. It is not a secure unit, so people could easily walk out and get lost, there are few carers so there are often public areas (the lounge, the library etc) where residents have no-one watching over them to make sure that they are not having problems and the entrance hall has large plants in pots which would be an open invitation for people with advanced dementia to wee into!
The home that mum was in was very different. It was quite shabby and looked outdated so that I had originally discounted it in my mind. Actually it was the best place for her as the care was excellent. There were always staff members around who knew exactly how to cope with dementia. Mum was coxed into having a shower and putting on clean clothes within 48 hours of being there and nothing fazed them. Mum got angry and hit one of them with her walking stick soon after she moved there and I was horrified, but they just shrugged if off as "one of those things". It was also a secure unit so mum couldnt walk out and get lost. She was very happy and thrived there and she lived there for three years, tending to her through her last days.
It is also worth looking at the other residents and seeing what stage of dementia they are at as this will tell you what stage they cannot cope with. In OH respite home none of them have obvious dementia symptoms (although Im sure a lot of them do have some dementia), but in mums home there were people at very advanced stages too. It is also worth asking what sort of behaviour they could not cope with. This will give you an idea of when you will have to move her.
Dont worry about the age difference. OH is the youngest in the home by many years (he is 63), but does not seem worried about the age gap.