leaflet.js

// Set zoom for leaflet map on specific pages.
$(document).bind('leaflet.map', function(e, map, lMap) {
  // Zoom out map on specific node pages.
  if ($('body').hasClass('node-type-YOURNODETYPE')) {
    lMap.setZoom(10);
  }
});

leaflet.php

<?php
/**
 * Implements hook_leaflet_map_info_alter()
 */
function mymodulde_leaflet_map_info_alter(&$maps) {
  // Prevent zooming by scroll.
  $maps['google-roadmap']['settings']['doubleClickZoom'] = FALSE;
  $maps['google-roadmap']['settings']['scrollWheelZoom'] = FALSE;
  // Set zoom level for all maps.
  $maps['google-roadmap']['settings']['zoom'] = 15;
}
?>