Try:
<?php
$rsRecips = new WA_MySQLi_RS("rsRecips",$connRIBIT_i,0);
$rsRecips->setQuery("SELECT CONCAT(rotarians.FirstName, ' ', rotarians.Surname)AS RecipName FROM rotarians WHERE rotarians.MemEmail IN (?) AND ClubID=? AND rotarians.status=0 ORDER BY rotarians.Surname");
$rsRecips->bindParam("sl", "".(isset($_POST['toEmail'])?$_POST['toEmail']:"-1") ."", "-1"); //p1
$rsRecips->bindParam("i", "".$_SESSION['ClubID'] ."", "-1"); //p2
$rsRecips->execute();
?>