B.L.
I know where you are coming from but sometimes no matter what and how nice are intentions are (concerning visitations)they fall on deaf ears. You have to let your son's father know that your son is in a routine that can not be interrupted on a whim. If he can not give you the date and time he will be picking up the baby then he can not pick him up at all. These type of men (my ex included) do not realize that we need to work as a team for our children. Just because we are no longer married doesn't mean that we can not work together on things concerning the children (i.e., vacations, school events, major decisions...)
Have you ever considered filing for full custody?
My ex has seen his children 3 times in the past year. He uses the excuse that he just doesn't have the money to drive up (he has the money and time to spend with his girlfriend but not with his children) Anyway, I just spend as much time as I can with them and I never tell them he is coming - I let it be a surprise because if they don't know he's coming then they won't be disappointed if he doesn't show up. I also make sure I call him every other week to let the girls talk to him and if doesn't pick up then I leave a message reminding him to call them. It sucks but that is the only way it works for me.
Some men just don't get what it entails to be a father (near or far). Raising children is not easy. They don't realize that they can still be good fathers even if they don't live close by. They can call, send a card, or even send presents.
I am sorry I seem to have gotten off the subject. I think you should put your foot down and let him know that this is how it is going to work. If doesn't call back and let you know when to expect him they he might as well not even bother. He needs to respect you as your son's mother and there are certain rules that need to be upheld regarding visits.
I hope I was a little helpful in your situation.