We went raspberry picking last week and it was a hit with the girl. She loved it - she got the hang of picking the ripe raspberries right away. She also got the hang of stuffing them immediately into her mouth. She was a girl on a mission, and her goal was to eat as many as she could. It was so fun to watch her while my mom and I picked.
The farm where we picked was about a 30 minute drive (we spent longer in the car than actually picking), it wasn't cheap - there was an "admission" fee (perhaps to pay for all the berries you inevitably eat while you're picking??), and then the raspberries were $4 a pint, and the sun was out in full force with no shade to be found... but it was worth it. We made some fun memories, and we all enjoyed ourselves.
(and we got some yummy raspberries, too!)
As a toddler activity, I would highly recommend berry picking - as long as you go on a day when it won't be crowded. It was nice that Eliza could walk up and down the rows without us having to be RIGHT next to her. She had some freedom, which I think helped a lot. Also, bring a hat and sunscreen. One other nice thing about berry picking is that you don't need to pack a snack!