Hi,
I made a test with your actual configuration where "Friday" and "Saturday" are excluded.
I select "Sunday" and the date as been approved correctly.
In order to test, I do not check the checkbox at the bottom so I do not validate the order and I can see if there is a warning message for the datepicker, or not.
And in my test, I just got the message
Message
Please make sure that you have selected the correct Location and Date Pick up
And the date is right stored in the date picker.
Please note that the "default today" is also working fine now.
During my test, the selected date was "16-11-2014" which is the correct one regarding the configuration.
Regards,