I would probably spend it on youth Go promotion - get 'em while they’re young!
Sponsorship of a youth Go team - team t-shirts/hoodies, travel costs for attendance at Go tourneys/camps.
Establishing Go in countries where it is less known - Greece? Other egf associate member countries? By provision of equipment for new clubs there maybe. Cost of school outreach sessions?
Contribute to a youth safe go server? BGA were looking into this. Especially for younger players, having somewhere to play that feels safe to parents/schools would be great.
The problem will be finding people (volunteers) through which to spend the money. My thoughts (far from original) all rely on someone to actually do the promoting/coordinating/teaching.