I think you're overthinking it. If you need a script to regularly get disk utilization ansible is overkill at best. You could use pssh to accomplish the same thing. The email part of this is a separate beast altogether.
```
ansible all -i inventory/your-machines -a "df -h" > output.txt
mailx -a output.txt -s "Disk Report"
us...@domain.com```
If you really wanted to waste your time you could include mailx in a playbook as a local_action.