Ansible - How to loop and get attributes of new EC2 instances - amazon-ec2

Question

I'm creating a set of new EC2 instances using this play
- hosts: localhost
connection: local
gather_facts: False
tasks:
- name: Provision a set of instances
ec2:
assign_public_ip: yes
aws_access_key: XXXXXXXXXX
aws_secret_key: XXXXXXXXXX
group_id: XXXXXXXXXX
instance_type: t2.micro
image: ami-32a85152
vpc_subnet_id: XXXXXXXXXX
region: XXXXXXXXXX
user_data: "{{ lookup('file', '/SOME_PATH/cloud-config.yaml') }}"
wait: true
exact_count: 1
count_tag:
Name: Demo
instance_tags:
Name: Demo
register: ec2
- name: Add new CoreOS machines to coreos-launched group
add_host: hostname="{{ item.public_ip }}" groups=coreos-launched
with_items: "{{ ec2.instances }}"
- name: Wait for SSH to come up
wait_for: host="{{ item.public_dns_name }}" port=22 delay=60 timeout=320
with_items: "{{ ec2.instances }}"
Now, I need to create an SSL/TLS certificate for every of those new machines. To do so, I require their private IP. Yet, I don't know how to access the "{{ ec2.instances }}" I registered in the previous play.
I tried something, in the same playbook, to do something like this
- hosts: coreos-launched
gather_facts: False
tasks:
- name: Find the current machine IP addresse
command: echo "{{ item.private_ip }}" > /tmp/private_ip
with_items: "{{ ec2.instances }}"
sudo: yes
But without any success. Is there a way to use the "{{ ec2.instances }}" items inside a same playbook but in a different play?
-- EDIT --
Following Theo advices, I manage to get the instances attributes using
- name: Gather current facts
action: ec2_facts
register: ec2_facts
- name: Use the current facts
command: echo "{{ ec2_facts.ansible_facts.ansible_ec2_local_ipv4 }}"
with_items: "{{ ec2_facts }}"

Answer 1

The best way to learn about a return structure (short of the documentation) is to wrap it in a debug task.
- name: Debug ec2 variable
debug: var=ec2.instances
From there, follow the structure to get the variable you seek.
Also (following the idempotence model), you can use the ec2_remote_facts module to get the facts from the instances and call them in future plays/tasks as well.
See Variables -- Ansible Documentation for more info about calling registered variables.