Treat it just like a job resume. You can tweak it to not have to be about jobs.
Example: you volunteered at your child's elementary school as yearbook salesperson
for the place, you'd put the school. for the job, salesperson. list any responsibilities you may have had (soliciting sales, managing the till, handwriting a receipt, etc). Put what year(s) you did this, and if you sold the most yearbooks- put that in there! highest sales! where you would normally put in salary, just put volunteer hours. instead of listing a supervisor, list a contact person they can call to verify this information if they need to.
For a cover letter, I would word it something along the lines of how you've spent 19 years using your skills to serve your community and family and you would like the opportunity to serve this company.. etc.
the main point of a resume is to allow the person to skim over the paper and get an idea of your skills and what you can do, and sometimes even a little bit of personality. As long as you follow a similar format, you can present yourself in a way that is just as appealing as someone who has been in the work force.