Get specific information from multi-dimensional array

Let say I have a array in this format:

[{"id":"11","children":[{"id":"9"},{"id":"5", "children":[{"id":"4"}]}]},{"id":"10","children":[{"id":"7"}]}]

And now I would like to get all ID's that are apparent in this array:

11,9,5,4,10,7

For that I would use a recursive code similar to this one:

ids = []

def find_ids arr
 arr.each do |entry|
   ids << entry["id"] if entry["id"]
   find_ids(entry["children"]) if entry["children"]
 end 
end

What would you do to get the ids?

Do you maybe know a really short version?

Thanks