I have a Sim living in a small house on the lot next to the festival center and noticed that they happen pretty frequently. But you have to be looking for them because they aren't announced. I wish they were though because my Sims that live on lots that aren't near the festival center never know when one is happening.
Some of the festivals, like the one that has two food stalls, have about 8 to 10 islanders attending. That one I'd like to do again because the Sims were having fun. I've only seen that one twice. The second time both food stalls were closed.
The other festivals seem to have kind of low turnouts. I saw 6 Sims at a festival where someone had made some roast pork, 4 Sims at the festival that has one easel and one guitar, and 1 Sim at a festival that was playing music and had several empty tables.
I think I saw the start of Family Fun Day once. I spotted three children dressed in coats and hats running to the beach. That's what caught my attention. I looked for them in Manage Worlds so I could change their outfits and found that none of them had a parent or parents. They all have families now.
There's a bonfire that appears near the fishing pier at night, along with two picnic tables and two lounge chairs. That little beach party seems to attract more Sims than the regular festivals. I've seen 6 to 8 Sims there each time.
Thanks @Hearts4u for posting the schedule!
