Well, this is for a learning environment for children, so I'd argue getting a language with a good hook is important. Additionally, both environments also offer

Well, this is for a learning environment for children, so I'd argue getting a language with a good hook is important. Additionally, both environments also offer a more interesting language under the hood to poke at -- for scratch, smalltalk/actionscript, and for logo, the lisp-style language under the hood -- to teach the more advanced concepts. Give interesting, easy results, but then use that to build on how to bring in more and more in-depth concepts.