For Ansible specific questions, I recommend asking in the Slack channel: https://netapppub.slack.com/archives/C2LUVV33R. They will have better knowledge of the best way to do this with the Ansible modules.
As far as REST goes, I thin you should be able to reboot all of the nodes at one time with a request like this if you wanted to:
PATCH /api/cluster/nodes?name=*&action=reboot&allow_data_outage=true
