Shortening substitute (1 Viewer)

[MysteryGenius]

So I'm planning on making unicorn poop with a kid I'm babysitting on the weekend and the recipe for the sugar cookie dough asks for "3/4 C shortening [1/4 C] (part butter [1/2C])".
I haven't had much experience with this, so I was wondering if I could substitute it with butter or vegetable oil or something? And how much would I use?