hmm i really like hummel but he occupies a strange place in the classical to romantic practices shift, a bridge composer sort of, unlike Beethoven he didn't really get too dramatic with the hamonies and style of writting but definately began to experiement with extended sonata forms, i.e. thinking on a larger more serious scale, as such he is both close to Haydn and Mozart and early Beethoven, and sort of in some regards some Romantic composers. if you decide to lead with the sonata, I think going late 19th century (i.e. late romanticism) to modern i.e pre world war I will give you a nice contrast and balance.
there's so much variety and options to choose from there that i'd first let your ear and heart decide what you like first then see how it fits your programming requirments and norms. if you're allowed (i.e is this for a school etc?), don't overlook transcriptions as those open up even more options (though probably staty away from concerto solo transcriptions since the form will be more inline with your hummel).
as closing with hummel, if you follow chronology in your recital youd be limited to pretty much baroque muisic, i'd explore CPE Bach works, really like him, but you could also look to later works that nod to baroque common forms, i.e. modern/romantic preludes and fuges, etc.
Topic: Recital Suggestions: Hummel Op. 81 Sonata