You cannot disable weekends on the date picker. If the user selects a weekend date and that will not result in error. May I suggest using visibility to hide your tables/matrices based on the date they select?
In your table(s) properties, go to the table visibility option and use this expression:
=IIF(weekday(Parameters!YourParameterName.Value) = 1, TRUE,IIF(weekday(Parameters!YourParameterName.Value) = 7, TRUE, FALSE))
Add a textbox after your table(s), include an "error message" in the textbox to display for users if they select a weekend date. Go to the textbox property, visibility option and use this expression:
=IIF(weekday(Parameters!YourParameterName.Value) = 1, FALSE, IIF(weekday(Parameters!YourParameterName.Value) = 7, FALSE, TRUE))
I'm using nested IIF function in here but you can use SWITCH if desired.
The result is when a weekend date is selected, your textbox will be displayed with your message. Otherwise your table(s) will show.