I am so sorry! I think I saw on another post that your husband is a fals. so he really knows what he is dealing with.
I don't think you will be able to hide anything from the kids as it goes along, but you should look into a counselor for them. I know my youngest were 11 and 12 when their dad got it, and it was tough. I remember vividly my 13 yo asking after about the first year, when is daddy going to start walking again...that was when we told her never. sigh.
My kids have seen and done things they never should have because of this crappy disease. Over all, 3 of the 4 are ok with it and it is just part of life. the youngest sees a counselor and has had a lot more trouble handling everything.
I work my butt off trying to keep their lives somewhat normal--dad can not always come first ( but he usually does, lol). overall, I think kids learn compassion from seeing their parents face als together.