Go for raceboard.
They are suitable for triangle racing in all conditions so even if you don't have too many sailboards, you can race in the general boat races.
If you haveto set a special course and organise a special race it is much less likely to happen. Ther are sailing clubs all over the world having races every weekend. Why not just join in.
Most clubs have handicap systems so it doesn't matter what gear you have, you just race against who ever is ahead of you (boat or board), and keep working to improve yourself.