61.113 and 91.146 define what a charitable event is.
If it were me I would say no, not unless you have 500 hours, and even then you have to pay your pro rata share at minimum. If no payment to you for costs is involved then still a no since you dont have 500. With 500, then maybe... See below.

Since its not a charitable event raising money(lets say they are referring to cash) according to 91.146 you may not be bound by the 500 hour requirement. but its volunteer work which IMO may fall under "charitable event", and thus the 500 hour requirement. Regardless of money being raised or not. One could argue that volunteering (free work) is the same as raising money since the work being done is not being paid for, but has some monetary value, i.e. your time, service provided, safety etc.

The other question is, if as a volunteer would you qualify for PIC duties, just as a regualr employee could. 61.113 (b) (1) and (2). This allows you to be re-imbursed for costs. More details in 61.113

id call the FSDO for clarification if i were you.