you have 2 instances of the insert behaivcor on the page, one at lines 42 - 60 and again at lines 135 - 153
remove the second one.
you have one of the columns bound to a search session variable:
$InsertQuery->bindColumn("kids_program_volunteer", "i", "".$_SESSION['WADbSearch1_kids_pcms2_users_results1'] ."", "WA_DEFAULT");
and i dont see any binding for the User ID column, that should be bound to the user ID form element.