Wedding situation

I'm getting married Halloween weekend, originally the only people in the wedding party were going to be my fiancé's cousin(21) as a ring bearer and his cousin's girlfriend (23) as the flower girl. Well about a month ago they broke up, I waited 2 weeks(in case it was just a big fight), then asked my future sister in law(24) to be the flower girl. She picked out her dress and is excited. Now the cousin is back together with his girlfriend, so she is back in the wedding and to even out the wedding party my fiancé asked one of his best friends to be in the wedding...NOW his cousin said he doesn't want to be in the wedding 🙄. I told my fiancé that the wedding party and their roles need to get figured out because dresses, vests, and flowers need to be ordered and I don't want to spend hundreds on people that aren't going to be there. My fiancé doesn't want a best man or groomsmen, so what other options are there besides having 2 flower girls and 2 ring bearers?