I'm designing a poster to advertise my kids' school fete, which is a fundraising event for the school. Some of the fonts I'm considering are marked as free for personal use. Is fundraising generally considered commercial use? I am not personally profiting in any way, and designing the poster as a volunteer.

The poster is made to generate money. The fact that this money is not for you and that you don't get paid for your work is irrelevant. The use is commercial, to generate money.