Our elementary volunteer appreciation is handled by the school. They organize a luncheon and ask every teacher/staff member to makes lists of anyone who has volunteered in any capacity. They send invitations plus make general announcements inviting everyone to the volunteer luncheon.
It's organized as a come-and-go activity (nice for working parents). The principal usually purchases a main dish like the several of the party size lasagne pans. Then staff contribute salads and desserts.
At some point (or points) the principal does a little announcement about how much they appreciate all volunteers. Usually there's a certificate. My favorite is a colorful "check" they ordered payable for "One Million Thanks".
These are available from several sources. Here's one
link
purely as an example. (I've never used this company.) Some of the ideas in the previous posts are good also. The check is nice for a situation where you aren't sure of the numbers. Very easy to keep a stack of blanks and fill out more as you need.
Whether the school or the PTO hosts such an event, I'd recommend keeping it simple.
As a volunteer, I really liked this approach. Nothing overwhelming. No well-intentioned, but unnecessary trinket to find a place for (or worse - dust!). Simple, sincere - a token gift that makes the recipient smile and feel appreciated.
