Ah, that might need clarifying. The Python picture is suggesting the language is for children. But the Arc image is because Arc itself is a young language, not because it's simplistic or childish.
That said, I wouldn't recommend Arc, unless you specifically want to code for Hubski. Not only because it's young, but it's not widely used, and doesn't really offer any advantages over other LISPs.
I'd suggest picking whichever of those sounds the most appealing. They're by far the most widely used, and will be easier to find help and docs for.
I'd also think about looking into Erlang and Scala. They're functional but not LISPs, and definitely worth the consideration.