How to execute helper function after DOM is ready in meteor

I have a list of <li>'s which gets populated with a find() using Meteor.startup as you see below. Then I'm getting all the data attributes of these <li>'s using data() and putting it in an object and trying to return/console.log it so I can see if it works. But I'm getting null as a result.

    Meteor.startup(function () {
    Template.messages.lists = function () {
        var allitems = lists.find();
        return allitems;
    };
    var map;
    map = new GMaps({
        div: '#map_canvas',
        lat: -12.043333,
        lng: -77.028333
    });
    var lat = map.getCenter().lat();
    var lng = map.getCenter().lng();
    map.addMarker({
        lat: lat,
        lng: lng,
        draggable: true,
        title: 'Test',
        dragend: function (e) {
            $('#lat').val(this.getPosition().lat());
            $('#lng').val(this.getPosition().lng());
        }
    });
    console.log(getMarkers());
});


function getMarkers() {
    var coordinates = {};
    coordinates = $('li.message').data();
    return coordinates;
}

I tried the same in my console directly and it works - I get an object back - so I'm guessing that the DOM is not ready/populated before this function is executed.

I am having a hard time understanding the difference between things like Meteor.startup and Template.mytemplate.rendered. In this case it seems that none of them works as I want?

What's the right way/place to do stuff with the DOM (traversing,getting attributes,manipulating)?

edit

as the code changed a lot in order to do what I wanted I post the whole thing.

Meteor.startup(function () {
  var map;
  map = new GMaps({
    div: '#map_canvas',
    lat: 50.853642,
    lng: 4.357452
  });
  Meteor.subscribe('AllMessages', function() {
    var allitems = lists.find().fetch();
    console.log(allitems);
    allitems.forEach(function(