For a sleepover me and my friend wanna watch...?

Zombieland and Shaun of the dead. I have seen both of them before at my dads house and i think they are HILARIOUS i havent seen them in awhile though, and raine saw zombieland abt 2 weeks ago but wants to watch shaun of the dead and zombieland again, the only problem though is im afraid my mom will say no cause we rlly want to watch it and we are only 13 and its rated R, except i've seen rated R movies with my mom but they are usually just for swearing and stuff like that not gore, what should i do?