Roaming around garden -anything dangerous I should think about?

Just let our two 11 week olds out into my garden today. They'll be moving up to their permanent home in the school where I am Head at the end of August, but their 9-ft run in our garden seemed too small for them so I let them out. The garden is secure (we have a dog) but not particularly chicken friendly (though I am not sure what that is anyway). They seem to peck at everything - what if something growing is poisonous to chickens? Should I be worried?
Fortunately frequent supervised contact since they were a week old with our dog has meant that he is as gentle as anything with them (though he is always very naughty in that he chases rabbits and sheep) and it was highly amusing to see one of them steal his dog chew today, right from under his nose! The cat also sees that they are superior to her and leaves them alone.
I have spent a glorious afternoon sitting in the garden ensuring they were safe, and will put them back in the run tonight. Only obvious problem seems to be their desire to get into the house!
Anything I should be worried about? We do have kites in the area - would they be interested??