How to deal with a spouse who won't advocate for your parent with Dementia

My mother's husband is standing in the way of every suggestion I have that would help my mother stay active and deal with some important things that are affecting her because of her dementia. She is still kind, social, funny, can hold great conversations, remember lots of things, and in my opinion needs help with some things at this point that he won't help her with or just doesn't think are necessary. Not too mention he is much older and this would take a lot of burden off of him. I live 3 hours away and try to visit for a 2 -3 days a couple times a month and help in any way I can but it's hard to do much on a quick visit. I have 2 brothers that can't seem to bring themselves to make an effort to help ! I would like to hire someone initially 3 mornings a week to get her out of the house to walk, go to a senior yoga class, take a drive, run out for groceries, remind her to take her appetite medicine, vitamins and to bathe on the mornings she is there. I don't know where to turn to find someone or if I can force him to let me do this without him retaliating by changing his will or something hateful like that, that could potentially affect her down the road.
Any advice would be greatly appreciated !!!