(This is only a comment.)  If you instead look at the family $\{x^d-x+n\}$, then it is known that there are infinitely many irreducible elements (for each positive $n$).  It suffices to show that $f(x)=x^p-x+n$ is irreducible in $\mathbb{F}_p$ for any prime $p$ such that $p\nmid n$. This is similar to a homework problem often assigned from Dummit and Foote's "Abstract Algebra" textbook, which is also solved by David Speyer here: [Is $x^p-x+1$ always irreducible in $\mathbb{F}_p$?][1]  The proof with $1$ replaced by $n$ is unchanged.

I suspect that the example family you gave also is known to contain infinitely many irreducible elements.




  [1]: https://mathoverflow.net/questions/167613/is-xp-x1-always-irreducible-in-mathbb-f-px