I hope you are well today and thank you for your question.
I am not sure what you meant by “only so it breaks up the font monotony on the page” but you can change your Navigation Menu font to “Courier New” by adding the following CSS code in the Custom CSS option of your theme on the below path.
Admin Area -> Appearance -> Customize -> Travelify Other Options
#main-nav li {
font-family: "Courier New", Courier, monospace;
}