And what I see is that area food banks, educational support organizations, mental-health providers, museums and others in the nonprofit arena advertise as they are able. They advertise for their annual fundraising galas, golf outings, benefits, etc.
While it might be a good idea to seek independent counsel from a lawyer about this, I'd imagine that any constraints would come from your own charter or board, rather than from outside sources.
Best of luck in sorting this out!
As president of Pomona, N.Y.-based marketing-advantage and founder of WomenCentric, Pattie Simone empowers ambitious women, companies and entrepreneurs worldwide, sharing smart new media, client engagement, entrepreneurial and communications expertise as a techpreneur, consultant, speaker and video blogger.