what really interests me is they can search by date range, eg: Entering the page and there are many courses but want some that match my vacation and I find from December 11 to February 15 all the courses available
As I can do to make the widgets have that option.
I would like to make that change me and make an extra payment for this work.
Well this is not possible specifically for the courses that starts in a particular interval .
But you can put those courses in a particular category and then can create a page showing these courses .
Use the page builder post grid block to show those courses from a particular category .
refer screenshot for the post grid page builder block settings :
http://i.imgur.com/HqI9W8k.png