Some sources say that "at the weekend" is wrong, while other ones say it's correct. Which form is acceptable in American English?

> 
> * On Saturdays her sister Ann usually comes to stay with Mary on/at/for/over the weekend/s.
> * What are you going to do at/on/for/over the weekend/s?
> * We are going to Paris on/at/for/over the weekend/s.
> * Are you going to stay here for/at/on/over the weekend/s?
> 
> 
> 

Which preposition do American English speakers use — *at*, *on*, *for*, *over*?