hi
@Charboo
welcome to posting
short answer is ... you can't
I appreciate that your husband wants to do all he can for his mother ... the 2 of you moving in with her and leaving your children is, though, a drastic way of managing the situation .... and doesn't seem to be making anyone 'happy'
sadly, your mil is unlikely to be happy with any arrangement, the dementia will simply require more and more from those who care for her and she's probably not going to show any gratitude or appreciate anyone else's perspective ... it's not you 'forcing' her into a move, it's a result of the demands of the dementia
your moving in with her may be the way to show your husband that his mother needs full time care and that it's too much to ask you to provide this ... I doubt he is happy; he's trying to put off the inevitable, and imo at the expense of your family life
your children aren't babies, but they are still young to be left to live by themselves to run the family home ... maybe they will learn how to look after themselves ... though it's hard on them, especially with winter and Christmas coming up
and it's tough on you, wanting to be with them
maybe start looking at local residential dementia homes so you have an idea of what might bs suitable, and even put your mil's name on thd waiting list of a couple ... better to be prepared than hit a crisis
and do have an assessment of her care needs and a care package put in place ... you may be living in her house but that doesn't mean you have to forgoe home care visits, day care and respite which are to take the strain off you and give you the chance to spend time with your children
also have a carer's assessment for yourself ... and look into Attendance Allowance and Carer's Allowance