What are peoples views on informing their ex of 11 years when their children are ill/hospital appointments?

I divorced 11 years ago and subsequantly have re-married, I have three children to my ex-husband one of them handicapped. My husbands partner of the last 10 years still stipulates that I cannot call him or have any contact with him otherwise she gives him a hard time. My ex only wants me to call him between the hours of 9 - 5 or keep it till he picks the kids up every other week. Am I being un-reasonable in calling at 5.55pm to tell him we are on our way to casualty. He admits she dislikes the children but keeps them away from her whilst the are on visits. I`m a little perplexed at peoples demands on partners with children and did wonder if others shared my disbeliefs or was I a one off?