$250 is a lot of money. I've been treasurer for 4.5 years, filed 8 years of Form 990 and got our 501c3 status (and got a waiver of $11k in fines for our failure to file 990s for many years), and we probably would have had to pay a lot more than $250 to have an accountant do that stuff ... but still, I wouldn't want a $250 gift. I did it all for the kids & the school.
That said, our PTO does usually give $25 gift cards to outgoing board members. And one president gave thank-yous out of her pocket to board members she'd worked with.
If you want to do something more, then I'd think about how you could do something to benefit the school with a plaque saying it was in honor of this person's efforts. Eg, if she helped with the playground, then put her name on a bench.
- gjcoram
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