I gave my chickens a cuke sliced in half like this. They LOVED it, but had the runs that night. So I limit cucumber to some chopped bits or the scooped out seeds. They love the "guts" of melons too.I do the same. Slice them lengthwise and let them clean it out leaving a shell of the skin.
And cherry tomatoes... what a show! "Who's got the red ball?" Me! No, me! Haha, you dropped it, it's mine... All around the run.
Instead of lettuce, I put various greens in a suet cake holder and hang that up in the run. Kale, spinach, weeds... They love that too.