Você deve poder adicionar a instância a um grupo com add_host e criar um inventário na memória.
- name: Add instance to host group
add_host: hostname={{ item.DnsName }} groups=cloud_formation
with_items: stack.stack_outputs
- name: Wait for SSH to come up
wait_for: host={{ item.DnsName }} port=22 delay=60 timeout=320 state=started
with_items: stack.stack_outputs
- name: Run your play
hosts: cloud_formation
----- your play here -------