The form "*I'll be closing the order book*" emphasizes that this is a future event, as the form " I'm closing the order book f" does not.

Also "*as we will go into the weekend*" seems odd or unnatural to me. I would suggest one of:

> * as the weekend starts   
> * as we are starting the weekend    
> * as the weekend begins
> * for the coming wqeekend

But the form "we will go" just does not seem to fit this context.