I have always found polish notation simple because it is so consistent.

The problem seems like the problem with Clojure (instead of say Racket) would be the uninformative error messages.

One problem is that kids, at least in the UK, are taught to say "one plus one" not "plus one one".

Sure, but when I was new to Lisp, I mentally read it as "add one to one". The first element of the expression is a verb, not a preposition.

This might be good thing to discuss in a tutorial aimed at kids.

My kids get very easily used to the lisp notation where the operator is always on first position