can I pick up my step son if its my husbands weekend and he's working
Yes... You are an official guardian to that child. His ex might be mad about it, depending on how they get along, but it is perfectly legal for you to pick him up.
Go for it...Why not?
Unless there's a specific court order against you, I see no problem with that. Especially if it was already discussed between you and your husband (i.e. not you just making your own decisions on the child.)
I think you should be asking your husband about this. Have him talk to his ex wife. They should be able to come up with an answer. I personally wouldn't have an issue with this if I was the ex;)
As long as there is no orders against you, yes. But you need permission from one or the other before you do anything.