Our family dynamics are changing because of my dad's failing health. Help?

My dad has Alzheimer's and my siblings live far away. My mom and I take care of my dad. When my siblings come down, they try to "push" their way and the in-laws try to meddle also. Of course, my siblings side with their spouses and this creates a nice mess. We try to be affirmative, accept some ideas if they seem reasonable, etc. but there seems to be a lot of competition and stress between my siblings. We used to get along so nicely. How do I deal with this? Any ideas?