Twin Gender Reveal

My husband and I were offered to have Materni21 test done to check for fetal abnormalies and the plus side is you can find out gender. Since we are having fraternal twins it will only be able to tell us if it's two girls if the X chromosome is present but if the Y chromosome is present it means we could be having one boy one girl or two boys haha so we won't officially know until I'm far enough to tell on a scan. Would you still find out ? I could atleast start shopping haha. At first I wanted a huge gender reveal party but now since we have this option I'm kinda considering having them put the results in a envelope and dropping it off at Publix and have them make a cake and me and hubby and cut it together. What is y'all opinions?