add an option with a blank value:
<option value="">show all</option>
and in the recordset SQL edit the condition to use a second OR comparison for -1 = newPerameter.
for example, you curently have the condition in the SQL for:
kids_program_time.id IN (WAQB_Param1)
and the WAQB_Param1 variable has the run time value set to use the time URL variable
adit the SQL To:
(kids_program_time.id IN (WAQB_Param1) OR -1 = WAQB_Param1_2)
then create another varaiable using the same settings as WAQB_Param1 variable but named WAQB_Param1_2, in the WAQB_Param1_2 variable, don't check the Comma separated list option.