TLDR: How would you monetize a mid-sized audience of consumers on an event discovery website?

Longer Version:

We are a small, bootstrapped startup that has built our audience up over the last 5 years while working on it nights/weekends. We now get a large amount of traffic in September and October - the trailing 31 day analytics count is just over 1 million visitors. Most of the visitors are looking for events.

Our monetization options are:

eCommerce - We initially tried eCommerce selling Halloween costumes. It was pretty time consuming, inventory goes out of stock all the time, and it is a once a year purchase that is not monthly recurring. When we had trouble growing our traffic of costume purchasers, we put it on the back burner.

Advertising - The obvious monetization method now is to sell advertising. In our case, this could mean large corporations targeting our audience or it could mean events that would purchase a featured/premium advertisement to consumers in their area.

Business Services - We could take the next 6 months, talk to the events that we currently drive traffic to, and try to build a product for them.

The obstacles: We don't have much (if any) money to put into the venture right now. We probably don't have bandwidth to do more than one at a time.

The good things: Traffic is growing about 50% year-over-year. We really don't need much money to be able to continue to grow. If we could get revenue on an interim basis to $50-100K/year, we'd be very happy.

I'd love to hear thoughts on how to tackle monetization.