I've solved the problem of converting the coordinates from 32610 in metres to WGS84 in the process of prepping the data for insertion into the MySQL dbs. This is the script:

/* This file is designed to be run against a series of GeoJSON 
 * files to create SQL statements which insert polygon and 
 * area information into our Land Title Databases. */
 
/* The GeoJSON files are generated from QGIS. */

// We need fileio and proj4 for coordinate conversion.
var fs = require("fs"), content, i, maxi, j, maxj, k, maxk, l, maxl, 
              gj, output, id, area, pathBits, outFile, arrCoords,
              degreeCoords, coords, ids=[], idList='',
              idCheck='', vancouverFiles=[], 
              mapleRidgeFiles=[], proj4 = require("proj4");
              
//We create these Proj4JS definitions so we can more easily refer to them later.
proj4.defs('epsg32610', '+proj=utm +zone=10 +ellps=WGS84 +datum=WGS84 +units=m +no_defs');
proj4.defs('WGS84', "+title=WGS 84 (long/lat) +proj=longlat +ellps=WGS84 +datum=WGS84 +units=degrees");

//GeoJSON files

//Two sets of data are for properties in the Vancouver db.
vancouverFiles.push('KitsilanoPlans/MergedKitsilano/MergedKitsilano_geom.json');
vancouverFiles.push('PowellStreetPlans/MergedPowellStreet/MergedPowell_geom.json');

//Three sets are for properties in the Maple Ridge db.
mapleRidgeFiles.push('MapleRidgePlans/MergedMapleRidge/MergedMapleRidge_geom.json');
mapleRidgeFiles.push('SaltSpringPlans/MergedSaltSpring/MergedSaltSpring_geom.json');
mapleRidgeFiles.push('StevestonPlans/MergedSteveston/MergedSteveston_geom.json');

console.log("\n *START* \n");

processFileArray(vancouverFiles, 'vancouver.sql');
processFileArray(mapleRidgeFiles, 'mapleRidge.sql');

//Process an array of files, creating a single output file
//with SQL commands to set the coordinate and area fields.
function processFileArray(files, outputFile){
  output = '';
  for (i=0, maxi=files.length; i<maxi; i++){
      ids = [];
      content = fs.readFileSync(files[i]);
      console.log('Read in ' + files[i] + '.');
      gj = JSON.parse(content);
      console.log('Found ' + gj.features.length + ' features in the file.')
      for (j=0, maxj=gj.features.length; j<maxj; j++){
//The UID is the value of the prp_property_id field in the database props table.
        id = gj.features[j].properties["UID"];
        if (id !== null){
//Keep a list of ids so we can do some checking later if necessary.

          ids.push('"' + id + '"');
        
//The area in sqm needs to be rounded to two decimal places.
          area = Math.round(parseFloat(gj.features[j].properties.area) * 100) / 100;
          
//Here we convert the original coordinates from 32610/metres to WGS84 (for GeoJSON).
          arrCoords = gj.features[j].geometry.coordinates;
          for (k=0, maxk=arrCoords.length; k<maxk; k++){
            for (l=0, maxl=arrCoords[k].length; l<maxl; l++){
              degreeCoords = proj4(proj4('epsg32610'), proj4('WGS84'), arrCoords[k][l]);
              //console.log(JSON.stringify(arrCoords[k][l]));
              //console.log(JSON.stringify(degreeCoords));
              arrCoords[k][l] = degreeCoords;
            }
          }

          coords = JSON.stringify(gj.features[j].geometry.coordinates);
          
//Write the two update statements for this property record.
          output += 'UPDATE `props` set `prp_coords` = "' + coords  + '" WHERE `prp_property_id`="' + id + '";\n';
          output += 'UPDATE `props` set `prp_area` = "' + area + '" WHERE `prp_property_id`="' + id + '";\n';
        }
      }
      idList = '(' + ids.join(', ') + ')';
      idCheck = '#id check: \n\n# ' + 'let $ids := ' + idList + ' return for $i in $ids where not(//prp_property_id[. = $i]) return $i \n\n'
      
      //idCheck = 'CREATE TYPE id_nums AS TABLE OF NUMBER;\n';
      //idCheck += 'SELECT * FROM TABLE(id_nums(' + idList + ')) '
      //idCheck += ' WHERE NOT IN (SELECT `prp_property_id` from `props`)\n\n';
      output = idCheck + output;
  }
  fs.writeFile(outputFile, output, function(err){});
}

console.log("\n *EXIT* \n");