Will i get in trouble or kicked out if i get caught trying to buy a ticket to an R rated movie?

me and my friend are both 16 and tonight we are going to try to get in to see Bruno. i dont look old enough so im afraid when i buy the ticket theyre going to card me. should i just say nevermind i dont have my id with me? what if they sell me the ticket, then the ticket ripper person (lol whatever theyre called) makes me show id? cause my brother is over 18 and he got me in to see Tropic Thunder last year and they sold him 2 tickets at the window, and then they asked to see my id when they ripped our tickets. and my friend wants to get her younger brother and his friend in too, theyre 14. i dont think theres any way in hell we're getting in, lol but she insists they wont card us. will we get in trouble if we somehow get caught after we have the tickets, or is it the theaters fault for not carding us? and how do we get in without being carded (without sneaking in)