Ember context passed to a view - ember.js

Question

I'm trying to figure out what's wrong about sending action from parentView to one of its children view:
I've made a PhotoUploadView used to resize and then upload images; it adds canvas drawing the resized image in a div inside its template:
<div class="img-list">
//here the canvas will be added
</div>
The action "saveImages" in this view, acts like this:
var list = this.$('.img-list');
$.each(list.children(), function(index, value) {
//here the code to save
}
But this action is not called directly; because I need to save not only the images but also some records (an offer record and many products records, children of the offer; the images are associated to the product record);
So I have the action "save" on the parentView that is like this:
//save records
offer.save().then(function(savedOffer) {
newProducts.forEach(function(product, indexP) {
product.set('offer', savedOffer);
product.save().then(function(savedProduct) {
}
}
}
//save photos by cycling the PhotoUploadViews that are inside ProductViews that are inside the mainView
this.get('childViews').forEach(function(view, index) {
if (index >= 4) { //the childView from the 4th are the ProductViews
var productId = view.get('product').get('id');
var folder = 'offer-' + controller.get('model').get('id') + '/product-' + productId + '/';
view.get('childViews')[0].send('saveImages', folder, productId); //the first childView of a ProductView is the UploadView
}
});
Well, this works and save the images correctly when you add images to an existing offer with existing product; but when you are creating a new offer, it fails since the folder will becone "offer-undefined/product-undefined" because of course you must wait the records to be saved in order to get their ID;
So I'm trying now to move the send action into the .then callback of product save:
var childViews = this.get('childViews'); //the childView starting from the 4th are the productsViews
offer.save().then(function(savedOffer) {
newProducts.forEach(function(product, indexP) {
product.set('offer', savedOffer);
product.save().then(function(savedProduct) {
var currentPview = (childViews[4 + indexP]); //get the productView associated with the current product
var productId = savedProduct.get('id');
var folder = 'offer-' + savedOffer.get('id') + '/product-' + productId + '/';
currentPview.get('_childViews')[2].send('saveImages', folder, productId); //the object at index 2 of _childViews array is the photoUploadView
Here, the folder is built correctly but after sending action, the saveImages action crashes saying that list is undefined; trying to log the value of "this" inside "saveImages" I can see that also its value is undefined; Someone can please explain why calling the action from one point, it works, and calling it inside the .then callback of product save it doesn't?
I also would like to understand why in the first case I can do
.get('childViews')[0]
to get the PhotoUploadView, but in the second I must do
.get('_childViews')[2]
since using get('childViews) it doesn't work anymore; What is the difference between childViews and _childViews? And why _childViews has more elements than childView?