Welcome to DC!
My initial piece of advice on this would be to consider your audience and go slow. Liquor can be overpowering in some things.
You can use liquor in place of a portion of the liquid called for in the recipe. I myself would not go over 1/4 cup.
You can add a tablespoon or two in place of the vanilla as a flavoring. I sometimes use cognac or dark rum with good results.
You could flavor the frosting and stick with the original recipe for the cake.
In a sturdy cake recipe you can make a simple syrup by boiling together 2 part sugar, 1 part liquor and 1 part water. Use this to paint on the cupcakes when they are still warm.
I would test any of these ideas on my poor family before trying them on a larger audience.