Going fruit picking is a great way to get your kids outdoors and more connected with nature, they will love it as they will be able to eat the fruit. Giving them their own container to collect the fruit in, will give them a sense of purpose which they will enjoy too.
I've been twice with my boys so far this summer, we went blackberry picking in one of our local parks one day. The blackberries are out in abundance now, they seem exceptionally sweet and big this year. We picked enough to make a big blackberry crumble with, which my boys loved making just as much as picking the blackberries.
We also went fruit picking in a 'pick your own' farm on the outskirts of London, there we got to choose to pick from a variety of fruit: strawberries, raspberries, redcurrants and blackberries as well as vegetables, although we just picked the fruit. This was a really fun thing to do, apart from the fact that it poured with rain, including thunder and lightening! Below is a picture of my boys sheltering from the rain! We still had a good time despite the rain. We picked a big bucket of rasberries, blackberries and strawberries which we made a pavlova with.
I really recommend going fruit picking with children, it's a lovely and simple thing to do. Picking fruit directly from the tree or plant also always tastes so much better than when bought from a supermarket. Summer fruits are also easily accessible to small children and toddlers as they grow low down.
My advice would be, that if you go to a 'pick your own' farm, go early if possible, as we only went in the afternoon and most of the strawberries apparently get picked in the morning!
Pickyourownfarms.org.uk provides a list of fruit picking farms throughout the UK, you just need to click on your area and list will come up.
Alternatively you can always go foraging for wild fruits, especially blackberries, which grow everywhere.