How to change datepicker options based on a checkbox?

I have a JqueryUI datepicker on which I only want dates 5-days-out (or more) to be available. This works fine for that...

     var dateToday = new Date(); 
        $( "#datepicker" ).datepicker({
        minDate: '+1w', // your min date
        beforeShowDay: $.datepicker.noWeekends // disable weekends
 });    

I also have a checkbox that, IF CHECKED, essentially overrides the minDate and makes the minDate available TODAY's date (rather than a week out):

<input type="checkbox" class="lessThanFiveDays" value="1" name="less-than-5-days" />I need this earlier than the standard 5 business days   

I'm struggling with where the checkbox checking JQuery needs to go and in what order. Also, do I just check if the box is checked, or does the altering of the datepicker params need to happen on a "change" event on the checkbox.

This below is wrong, but hopefully it helps illustrate how I'm confusing myself:

$( "#datepicker" ).datepicker({
minDate: '+1w', // your min date
beforeShowDay: $.datepicker.noWeekends // disable weekends*/
});
 $('.lessThanFiveDays').change(function() {
    if($(this).is(":checked")) {
        $( "#datepicker" ).datepicker({
        minDate: dateToday, // your min date
        beforeShowDay: $.datepicker.noWeekends // disable weekends*/
        });
    }