I would advise a farmer to carefully consider how much relation there is between what she wants to do on the land and what she actively farms. There have already been parts of the law relaxed for having farm stands and other small business that supply farm goods directly to consumers. Also, small events that only last for a short part of the year (pumpkin patches, cider apple picking) seem to be okay. However, it seems as though the more people you want to bring on to the land, the more difficult it is and more likely that you will need a variance. Ultimately, the best advice would be to consult with the local government before making any major changes or starting new businesses on farm property. 

Here is a recent article from Pennsylvania. They are currently debating a state-wide bill to get rid of government restrictions on agric-tourism ventures. Like in Oregon, the side that is for the bill is arguing that small farms and holdings need these opportunities to stay afloat and that the restrictions are currently damaging those farms. The bill would allow any kind of agritourism (including music festivals and year-round weddings which are still limited in Oregon).