I'm not an attorney, so I can only offer my perception of what you should be able to do, based on what I see in the nonprofit community at large.

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!
Pattie Simone